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

namespace
{
bool b[ 110 ];
}

int main()
{
int i;
int j;
int iNum;
int N;
char A[ 50 ];

	cin >> N;
	for( i = 0; i < N; i++ )
	{
		for( j = 0; j < N; j++ )
		{
			cin >> A;
			if( i == j ) continue;
			if( b[ j ] ) continue;
			if( strcmp( A, "nyanpass" ) == 0 ) continue;

			b[ j ] = true;
		}
	}


	j = 0;
	for( i = 0; i < N; i++ )
	{
		if( ! b[ i ] )
		{
			j++;
			iNum = i + 1;
			if( j > 1 ) break;
		}
	}

	if( j == 1 )
		cout << iNum << endl;
	else
		cout << - 1 << endl;

	return 0;
}