#include <iostream>
#include <string>

using namespace std;

int main()
{
    int n;
    string x;
    cin >> n;
    for(int i = 1; i <= n; i ++){
        cin >> x;
        if(i % 3 == 0 and i % 5 != 0 and x != "BIMM"){
            cout << i;
            return 0;
        }
        else if(i % 3 != 0 and i % 5 == 0 and x != "BAMM"){
            cout << i;
            return 0;
        }
        else if(i % 3 == 0 and i % 5 == 0 and x != "BUMM"){
            cout << i;
            return 0;
        }
        else if(i % 3 != 0 and i % 5 != 0 and x != "SZAM"){
            cout << i;
            return 0;
        }
    }
    return 0;
}