#define _USE_MATH_DEFINES

#include <iostream>
#include <iomanip>

#include <algorithm>
#include <cmath>

#include <string>
#include <array>
#include <list>
#include <queue>
#include <vector>
#include <complex>
#include <set>
#include <map>

/////////
#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i,n) REP(i,0,n)
#define P(p) cout<<(p)<<endl;

#define PII pair<int,int>
/////////
typedef long long LL;
typedef long double LD;
/////////
using namespace::std;
/////////

int main(void){
    std::cin.tie(0); 
    std::ios::sync_with_stdio(false);
    std::cout << std::fixed;//
    cout << setprecision(10);//

	int N;
	string str[100][100];
	cin>>N;
	rep(i,N)rep(j,N)cin>>str[i][j];

	int ans[100];
	rep(i,N){
		ans[i] = -1;
	}
	bool flag = false;
	rep(j,N){
		flag = true;
		rep(i,N){
			if( i!=j && str[i][j] != "nyanpass"){
				flag = false;
				break;
			}
		}
		if(flag == true){
			ans[j] = 1;
		}
	}
	int count = 0;
	int at= -1;
	rep(i,N){
		if(ans[i] == 1){
			at = i+1;
			++count;
		}
	}
	if(count == 1){
		P(at);
	}else{
		P(-1);
	}
    return 0;
}