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

int main(void) {
	int i, j, k, N, renchon, meetings = 0;
	int suspects[100] = { 0 };
	char target[8] = { 'n', 'y', 'a', 'n', 'p', 'a', 's', 's' };
	char table[100][30];

	scanf("%d", &N);
	for (i = 0; i < N; i++) {
		for (j = 0; j < N; j++) {
			scanf("%s", &table[i]);

			if (strncmp(table[i], target, 8) == 0)
				suspects[j]++;
		}
	}

	for (k = 0; k < N; k++) {
		if (suspects[k] == N - 1) {
			meetings++;
			renchon = k + 1;
		}
	}

	if (meetings == 1) {
		printf("%d\n", renchon);
	}
	else
		puts("-1");

	return 0;
}