#include <iostream>

using namespace std;

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

	string in;

	for (i = 1; i <= n; i++)
	{
		cin >> in;

		if (i % 3 == 0)
		{
			if (i % 5 == 0)
			{
				if (in != "BUMM")
				{
					cout << i;
					return 0;
				}
			}
			else
			{
				if (in != "BIMM")
				{
					cout << i;
					return 0;
				}
			}
		}
		else
		{
			if (i % 5 == 0)
			{
				if (in != "BAMM")
				{
					cout << i;
					return 0;
				}
			}
			else
			{
				if (in != "SZAM")
				{
					cout << i;
					return 0;
				}
			}
		}
	}
	cout << 0;
}
//16
//SZAM
//SZAM
//BIMM
//SZAM
//BAMM
//BIMM
//SZAM
//SZAM
//BIMM
//BAMM
//SZAM
//BIMM
//SZAM
//SZAM
//BUMM
//SZAM