import std.stdio, std.string, std.conv, std.array, std.algorithm;
import std.uni, std.range, std.math, std.container, std.datetime;
import core.bitop, std.typetuple, std.typecons;

immutable long MOD = 1_000_000_007;
alias tie = TypeTuple;

void main(){
    auto N = readln.chomp.to!int;
    auto A = new string[][](N, N);

    foreach(i ; 0 .. N){
        A[i] = readln.split;
    }

    int cnt, ans;

    foreach(j ; 0 .. N){
        bool flag = true;
        foreach(i ; 0 .. N){
            if(i == j) continue;
            if(A[i][j] != "nyanpass") flag = false;
        }
        if(flag){
            cnt++;
            ans = j;
        }
    }

    writeln(cnt == 1 ? ans + 1 : -1);
}


void readVars(T...)(auto ref T args){
    auto line = readln.split;
    foreach(ref arg ; args){
        arg = line.front.to!(typeof(arg));
        line.popFront;
    }
    if(!line.empty){
        throw new Exception("args num < input num");
    }
}