using System;

public class Program {
    
    public static void Main (string[] args) {
        short n = short.Parse (Console.ReadLine ());
        short ans = 0;
        
        for (short i = 1; i <= n && ans == 0; i++) {
            string s = Console.ReadLine ();
            string sExpect = (i%15 == 0 ? "BUMM" : (i%5 == 0 ? "BAMM" : (i%3 == 0 ? "BIMM" : "SZAM")));
            
            if (sExpect != s)
                ans = i;
        }
        
        Console.WriteLine (ans);
    }
}