#include <stdio.h>
#include <string.h>

int main(void){
    int i, j, N, renchon = 0, cnt = 0;
    char s[31];
    scanf("%d", &N);
    int villager[101] = {0};
    for(i=1;i<=N;i++){
        for(j=1;j<=N;j++){
            scanf("%s", &s);
            if(!strcmp(s, "nyanpass")){
                villager[j]++;
            }
        }
    }
    for(i=1;i<=N;i++){
        if(villager[i]==N-1){
            renchon = i;
            cnt++;
        }
    }
    if(renchon!=0 && cnt==1){
        printf("%d\n", renchon);
    }else{
        printf("-1\n");
    }
    return 0;
}