diff --git a/day21/d21p1.swift b/day21/d21p1.swift
new file mode 100644
index 0000000..ef5f069
--- /dev/null
+++ b/day21/d21p1.swift
@@ -0,0 +1,106 @@
+import Foundation
+
+typealias Key = String
+let (nA, nEmpty) = ("A", "")
+let (n7, n8, n9, n4, n5, n6, n1, n2, n3, n0) =
+    ("7", "8", "9", "4", "5", "6", "1", "2", "3", "0")
+let (nL, nR, nU, nD) = ("<", ">", "^", "v")
+
+protocol Pad {
+    static func seq(_ k1: Key, _ k2: Key) -> Set<[Key]>
+}
+
+struct Numpad : Pad {
+    static let pos: [Key: (Int, Int)] = [
+        n7: (0, 0), n8: (0, 1), n9: (0, 2),
+        n4: (1, 0), n5: (1, 1), n6: (1, 2),
+        n1: (2, 0), n2: (2, 1), n3: (2, 2),
+                    n0: (3, 1), nA: (3, 2)
+    ]
+
+    static func seq(_ k1: Key, _ k2: Key) -> Set<[Key]> {
+        let (pos1, pos2) = (pos[k1]!, pos[k2]!)
+        let verKey = pos1.0 < pos2.0 ? nD : nU
+        let horKey = pos1.1 < pos2.1 ? nR : nL
+        let seqs: [[Key]] = [  // ???
+                Array(repeating: verKey, count: abs(pos1.0 - pos2.0)) +
+                Array(repeating: horKey, count: abs(pos1.1 - pos2.1)),
+                Array(repeating: horKey, count: abs(pos1.1 - pos2.1)) +
+                Array(repeating: verKey, count: abs(pos1.0 - pos2.0))
+            ].filter { seq in
+                (k1 != n1 || !seq.starts(with: [nD])) &&
+                (k1 != n4 || !seq.starts(with: [nD, nD])) &&
+                (k1 != n7 || !seq.starts(with: [nD, nD, nD])) &&
+                (k1 != n0 || !seq.starts(with: [nL])) &&
+                (k1 != nA || !seq.starts(with: [nL, nL]))
+            }
+        return Set(seqs)
+    }
+
+}
+
+struct Dirpad : Pad {
+    static let pos: [Key: (Int, Int)] = [
+                    nU: (0, 1), nA: (0, 2),
+        nL: (1, 0), nD: (1, 1), nR: (1, 2)
+    ]
+    static func seq(_ k1: Key, _ k2: Key) -> Set<[Key]> {
+        let (pos1, pos2) = (pos[k1]!, pos[k2]!)
+        let verKey = pos1.0 < pos2.0 ? nD : nU
+        let horKey = pos1.1 < pos2.1 ? nR : nL
+        let seqs: [[Key]] = [  // ???
+                Array(repeating: verKey, count: abs(pos1.0 - pos2.0)) +
+                Array(repeating: horKey, count: abs(pos1.1 - pos2.1)),
+                Array(repeating: horKey, count: abs(pos1.1 - pos2.1)) +
+                Array(repeating: verKey, count: abs(pos1.0 - pos2.0))
+            ].filter { seq in
+                (k1 != nU || !seq.starts(with: [nL])) &&
+                (k1 != nA || !seq.starts(with: [nL, nL])) &&
+                (k1 != nL || !seq.starts(with: [nU]))
+            }
+        return Set(seqs)
+    }
+}
+
+extension Pad {
+    static func press(_ start: Key, _ keys: ArraySlice<Key>) -> [[Key]] {
+        if keys.count == 0 {
+            return [[]]
+        }
+        return seq(start, keys[keys.startIndex]).flatMap { firstSeq in
+            press(keys[keys.startIndex], keys.dropFirst()).map { restSeq in
+                firstSeq + [nA] + restSeq
+            }
+        }
+    }
+}
+
+func readInput(_ filePath: String) throws -> [[Key]] {
+    return try String(contentsOfFile: filePath, encoding: .ascii)
+        .split(separator: "\n").map { Array($0).map(String.init) }
+}
+
+let answer = try readInput(CommandLine.arguments[1]).map { passwd in
+        Numpad.press(nA, passwd[...]).flatMap { dirSeq1 in
+            Dirpad.press(nA, dirSeq1[...]).flatMap { dirSeq2 in
+                Dirpad.press(nA, dirSeq2[...])
+            }
+        }.map { $0.count }.min()! * Int(passwd.joined().dropLast())!
+    }.reduce(0, +)
+print(answer)
+
+//}.forEach { line in
+//    print()
+//    line.map { $0.joined() }.forEach { print("\($0.count): \($0)") }
+//}
+            
+
+/*
+Numpad.press(nA, [n0, n2, n9, nA])
+    .map { $0.joined() }.forEach { print("\($0.count): \($0)") }
+print()
+Dirpad.press(nA, "<A^A^^>AvvvA".map(String.init)[...])
+    .map { $0.joined() }.forEach { print("\($0.count): \($0)") }
+print()
+*/
+
diff --git a/day21/input.txt b/day21/input.txt
new file mode 100644
index 0000000..f96709c
--- /dev/null
+++ b/day21/input.txt
@@ -0,0 +1,5 @@
+169A
+279A
+540A
+869A
+789A
diff --git a/day21/test.txt b/day21/test.txt
new file mode 100644
index 0000000..4cf0c29
--- /dev/null
+++ b/day21/test.txt
@@ -0,0 +1,5 @@
+029A
+980A
+179A
+456A
+379A