#include <bits/stdc++.h>
using namespace std;

int main() {
	int n;
    cin >>n;
    string bim="BIMM",bam="BAMM",bum="BUMM",szam="SZAM",most;
    for(int i=1;i<=n;i++){
        cin>>most;
        if(i%3==0&&i%5==0){
            if(most!=bum){
                cout <<i<<"\n";
                return 0;
            }
            continue;
        }
        if(i%3==0){
            if(most!=bim){
                cout <<i<<"\n";
                return 0;
            }
            continue;
        }
        if(i%5==0){
            if(most!=bam){
                cout <<i<<"\n";
                return 0;
            }
            continue;
        }
        if(most!=szam){
            cout <<i<<"\n";
            return 0;
        }
    }
}