#include <iostream>
#include <vector>
using namespace std;

int main()
{
	int n;
	cin >> n;

	vector<string>list(n + 1);

	for (int i = 1; i < n + 1; i++)
	{
		cin >> list[i];
	}

	int i = 1;

	n = n + 1;

	while (i < n) {
		bool div3 = (i % 3 == 0);
		bool div5 = (i % 5 == 0);
		std::string val = list[i];

		if ((div3 && div5 && val == "BUMM") ||
			(div3 && val == "BIMM") ||
			(div5 && val == "BAMM") ||
			(val == "SZAM")) {
			i++;
		}
	}
	if (i == n)
		cout << 0;
	else
		cout << i;
}

//i % 3 == 0 && i % 5 == 0) && list[i] == "BUMM"
//i % 3 == 0 && list[i] == "BIMM"
//i % 5 == 0 && list[i] == "BAMM"
//list[i] == "SZAM"