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

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