diff --git a/day11/src/main.rs b/day11/src/main.rs
index 543560c..e611da1 100644
--- a/day11/src/main.rs
+++ b/day11/src/main.rs
@@ -130,19 +130,23 @@ fn main() {
     loop {
         match parse_monkey(&mut lines) {
             Ok(None) => break,
-            Ok(Some(m)) => { assert!(m.id == monkeys.len() as u64); monkeys.push(m) },
+            Ok(Some(m)) => {
+                assert!(m.id == monkeys.len() as u64);
+                monkeys.push(m)
+            },
             Err(e) => eprintln!("{:?}", e),
         }
     }
     let mut monkey_item_counts = vec![0; monkeys.len()];
+    let lcd = monkeys.iter().fold(1, |acc, m| acc * m.div_by_test);
 
-    for _round in 1..=20 {
+    for _round in 1..=10000 {
         for i in 0..monkeys.len() {
             monkey_item_counts[i] += monkeys[i].items.len();
 
             for _item in 0..monkeys[i].items.len() {
                 let old_item = monkeys[i].items.pop_front().unwrap();
-                let new_item = monkeys[i].operation.perform(old_item) / 3;
+                let new_item = monkeys[i].operation.perform(old_item) % lcd;
                 let new_i = if new_item % monkeys[i].div_by_test == 0 {
                     monkeys[i].true_throw
                 } else {
diff --git a/day11/src/main1.rs b/day11/src/main1.rs
new file mode 100644
index 0000000..543560c
--- /dev/null
+++ b/day11/src/main1.rs
@@ -0,0 +1,158 @@
+use std::num::ParseIntError;
+use std::env;
+use std::fs::File;
+use std::io::{self, BufRead, Lines};
+use std::collections::VecDeque;
+
+#[derive(Debug)]
+enum Operator { Add, Mul }
+#[derive(Debug)]
+enum Operand { Old, Imm(u64) }
+
+#[derive(Debug)]
+struct Operation { left: Operand, op: Operator, right: Operand }
+impl Operation {
+    fn perform(&self, old: u64) -> u64 {
+        let left = match self.left {
+            Operand::Old => old,
+            Operand::Imm(x) => x,
+        };
+        let right = match self.right {
+            Operand::Old => old,
+            Operand::Imm(x) => x,
+        };
+        match self.op {
+            Operator::Add => left + right,
+            Operator::Mul => left * right,
+        }
+    }
+}
+
+#[derive(Debug)]
+struct Monkey {
+    id: u64,
+    items: VecDeque<u64>,
+    operation: Operation,
+    div_by_test: u64,
+    true_throw: u64,
+    false_throw: u64,
+}
+
+#[derive(Debug)]
+enum MonkeyError {
+    ParseError(),
+    ParseIntError(ParseIntError),
+    IoError(io::Error),
+}
+impl From<ParseIntError> for MonkeyError {
+    fn from(e: ParseIntError) -> Self { MonkeyError::ParseIntError(e) }
+}
+impl From<io::Error> for MonkeyError {
+    fn from(e: io::Error) -> Self { MonkeyError::IoError(e) }
+}
+
+fn parse_monkey<B: BufRead>(
+    lines: &mut Lines<B>
+) -> Result<Option<Monkey>, MonkeyError> {
+    let id = match lines.next() {
+        Some(line) => line?
+            .strip_prefix("Monkey ").ok_or(MonkeyError::ParseError())?
+            .strip_suffix(":").ok_or(MonkeyError::ParseError())?
+            .parse::<u64>()?,
+        None => return Ok(None),
+    };
+
+    let starting_items = lines.next().ok_or(MonkeyError::ParseError())??
+        .strip_prefix("  Starting items: ").ok_or(MonkeyError::ParseError())?
+        .split(", ")
+        .map(|item| item.parse::<u64>())
+        .collect::<Result<VecDeque<_>, _>>()?;
+
+    let op_line = lines.next().ok_or(MonkeyError::ParseError())??;
+    let op_vec = op_line
+        .strip_prefix("  Operation: new = ").ok_or(MonkeyError::ParseError())?
+        .split(' ').collect::<Vec<_>>();
+    let (left, operator, right) = (op_vec[0], op_vec[1], op_vec[2]);
+    let operation = Operation {
+        left: match left {
+            "old" => Operand::Old,
+            _ => Operand::Imm(left.parse()?)
+        },
+        op: match operator {
+            "+" => Ok(Operator::Add),
+            "*" => Ok(Operator::Mul),
+            _ => Err(MonkeyError::ParseError())
+        }?,
+        right: match right {
+            "old" => Operand::Old,
+            _ => Operand::Imm(right.parse()?)
+        },
+    };
+        
+    let test_val = lines.next().ok_or(MonkeyError::ParseError())??
+        .strip_prefix("  Test: divisible by ").ok_or(MonkeyError::ParseError())?
+        .parse::<u64>()?;
+
+    let true_throw = lines.next().ok_or(MonkeyError::ParseError())??
+        .strip_prefix("    If true: throw to monkey ")
+        .ok_or(MonkeyError::ParseError())?
+        .parse::<u64>()?;
+    let false_throw = lines.next().ok_or(MonkeyError::ParseError())??
+        .strip_prefix("    If false: throw to monkey ")
+        .ok_or(MonkeyError::ParseError())?
+        .parse::<u64>()?;
+
+    // Remove empty line if exists
+    match lines.next() {
+        None => Ok(()),
+        Some(Err(e)) => Err(e),
+        Some(Ok(s)) => Ok(match s.as_str() {
+            "" => Ok(()),
+            _ => Err(MonkeyError::ParseError()),
+        }?),
+    }?;
+
+    Ok(Some(Monkey {
+        id: id,
+        items: starting_items,
+        operation: operation,
+        div_by_test: test_val,
+        true_throw: true_throw,
+        false_throw: false_throw,
+    })
+)}
+
+fn main() {
+    let file = File::open(&env::args().nth(1).unwrap()).unwrap();
+    let mut lines = io::BufReader::new(file).lines();
+    let mut monkeys: Vec<Monkey> = Vec::new();
+
+    loop {
+        match parse_monkey(&mut lines) {
+            Ok(None) => break,
+            Ok(Some(m)) => { assert!(m.id == monkeys.len() as u64); monkeys.push(m) },
+            Err(e) => eprintln!("{:?}", e),
+        }
+    }
+    let mut monkey_item_counts = vec![0; monkeys.len()];
+
+    for _round in 1..=20 {
+        for i in 0..monkeys.len() {
+            monkey_item_counts[i] += monkeys[i].items.len();
+
+            for _item in 0..monkeys[i].items.len() {
+                let old_item = monkeys[i].items.pop_front().unwrap();
+                let new_item = monkeys[i].operation.perform(old_item) / 3;
+                let new_i = if new_item % monkeys[i].div_by_test == 0 {
+                    monkeys[i].true_throw
+                } else {
+                    monkeys[i].false_throw
+                } as usize;
+                monkeys[new_i].items.push_back(new_item);
+            }
+        }
+    }
+    monkey_item_counts.sort_by(|x, y| y.cmp(x));
+    println!("{:?}", monkey_item_counts[0]*monkey_item_counts[1]);
+}
+