#include <stdio.h>
#include <string>
int main(){
    //input
    int N;
    scanf("%d",&N);

    bool person[100];
    for (int i = 0;i < N;i++){
        person[i] = true;
    }
    for (int i = 0;i < N;i++){
        for (int j = 0;j < N;j++){
            char str[31];
            scanf("%s",str);
            if (i != j && std::string(str) != "nyanpass"){
                person[j] = false;
            }
        }
    }

    //count "true" person
    int renge;
    int count = 0;
    for (int i = 0;i < N;i++){
        if (person[i]){
            renge = i+1;
            count++;
        }
    }

    //output
    if (count == 1){
        printf("%d\n",renge);
    }else{
        printf("%d\n",-1);
    }
    return 0;
}