#include <iostream>

using namespace std;

int main()
{
    int length;
    cin >> length;
    length++;

    string current;
    for (int i = 1; i < length; i++) {
        cin >> current;
        if (i % 3 == 0) {
            if (i % 5 == 0 && current == "BUMM") {
                continue;
            }
            else if (current == "BIMM") {
                continue;
            }
            cout << i;
            return 0;
        }
        else if (i % 5 == 0 && current == "BAMM") {
            continue;
        }
        else if (current == "SZAM") {
            continue;
        }
        cout << i;
        return 0;
    }
}