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

int main(void)
{
	char a[101][101][31];
	int n;
	int i, j;
	int vno[101] = {0};
	int count = 0;
	int ans = 0;

	scanf("%d", &n);
	for (i = 1; i <= n; i++) {
		for (j = 1; j <= n; j++) {
			scanf("%s", &a[i][j]);
		}
	}
	for (i = 1; i <= n; i++) {
		for (j = 1; j <= n; j++) {
			if (!strcmp(a[i][j], "nyanpass"))
				vno[j]++;
		}
	}
	for (j = 1; j <= n; j++) {
		if (vno[j] == n - 1) {
			count++;
			ans = j;
		}
	}
	if (count == 0 || count >= 2)
		printf("%d\n", -1);
	else 
		printf("%d\n", ans);

	return 0;
}