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

int meg(vector<string> sek, int n) {
	string e;
	for (int i = 1; i <= n; i++) {
		if (i % 3 == 0 && i % 5 == 0)
			e = "BUMM";
		else if (i % 3 == 0)
			e = "BIMM";
		else if (i % 5 == 0)
			e = "BAMM";
		else
			e = "SZAM";
		if (sek[i-1] != e)
			return i;
	}
	return 0;
}

int main() {
	int n;
	string s;
	vector<string> sek;
	cin >> n;
	for (int i = 0; i < n; i++) {
		cin >> s;
		sek.push_back(s);
	}
	cout << meg(sek, n) << '\n';
}