#include <iostream>
#include <string>
#include <vector>
using namespace std;
int main(){
    string a="BIMM";
    string b="BUMM";
    string c="BAMM";
    string d="SZAM";
    int db=0;
    int n; cin>>n;
    vector <string> jatek(n+1);
    for (int i=1;i<=n;++i) cin>>jatek[i];
    for (int i=1;i<=n;++i){
        if (jatek[i]==c && (i%5!=0 || i%3!=0)){
            db=i; break;
        }
        else if (jatek[i]==a && i%3!=0){
            db=i; break;
        }
        else if (jatek[i]==b && i%5!=0){
            db=i; break;
        }
        else if (jatek[i]==d && (i%3==0 || i%5==0)){
            db=i; break;
        }
    }
    cout<<db;
    return 0;
}