use std::env;
use std::fs::File;
use std::io::{BufReader, Read};

fn main() {
    let file = File::open(&env::args().nth(1).unwrap()).unwrap();
    let reader = BufReader::new(file);

    let (mut x1, mut x2, mut x3) = (0, 0, 0);
    let mut i = 0;
    for byte in reader.bytes() {
        i += 1;
        let c = byte.unwrap();
        if c != x1 && c != x2 && c != x3
                && x1 != x2 && x1 != x3 && x2 != x3
                && x1 != 0 {
            println!("{}", i);
            break;
        } else {
            x1 = x2;
            x2 = x3;
            x3 = c;
        }
    }
}