#include <iostream>

using namespace std;

int main()
{
    int n, hol = 1, rossz=0,cucc=1;
    cin >> n;
    string x;
    for (int i = 1; i <= n and cucc==1; i++) {
        cin >> x;
        if (hol % 3 != 0 and hol % 5 != 0 and x == "BIMM" and cucc==1)
        {
            cout << i;
            cucc = 0;
        }
        
        if (hol % 3 != 0 and hol % 5 != 0 and x == "BUMM" and cucc == 1)
        {
            cout << i;
            cucc = 0;
        }
        if (hol % 3 != 0 and hol % 5 != 0 and x == "BAMM" and cucc == 1)
        {
            cout << i;
            cucc = 0;
        }
        if (hol % 3 == 0 and hol % 5 != 0 and x == "BUMM" and cucc == 1)
        {
            cout << i;
            cucc = 0;
        }
        if (hol % 3 == 0 and hol % 5 != 0 and x == "BAMM" and cucc == 1)
        {
            cout << i;
            cucc = 0;
        }
        if (hol % 3 == 0 and hol % 5 == 0 and x == "BAMM" and cucc == 1)
        {
            cout << i;
            cucc = 0;
        }
        if (hol % 3 == 0 and hol % 5 == 0 and x == "BIMM" and cucc == 1)
        {
            cout <<i;
            cucc = 0;
        }
        if (hol % 3 != 0 and hol % 5 == 0 and x == "BUMM" and cucc == 1)
        {
            cout << i;
            cucc = 0;
        }
        if (hol % 3 != 0 and hol % 5 == 0 and x == "BIMM" and cucc == 1)
        {
            cout << i;
            cucc = 0;
        }
        
        hol++;
    }
    //cout << rossz - 1;

    return 0;
}