#include<iostream>
#include<cstdio>
#include<vector>
#include<queue>
#include<map>
#include<string>
#include<algorithm>
#include<functional>
using namespace std;
#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n) for (int i=0;i<(n);i++)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
#define INF 1<<30
#define MP make_pair
#define mp make_pair
#define pb push_back
#define PB push_back
#define DEBUG(x) cout<<#x<<": "<<x<<endl
#define ll long long
#define ull unsigned long long

int main(){
	int n;cin>>n;
	vector<vector<string> > str(n,vector<string>(n));
	REP(i,n){
		REP(j,n) cin>>str[i][j];
	}
	int cnt=0;
	vector<int> ren;
	REP(j,n){
		bool f=true;
		REP(i,n){
			if(i!=j && str[i][j]!="nyanpass") {f=false;break;}
		}
		if(f){cnt++;ren.pb(j+1);}
	}
	if(ren.size()==1) {cout<<ren[0]<<endl;return 0;}
	cout<<"-1"<<endl;
}