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

int main(void){
	int r[128]={0},n,i,j,zr=0,c;
	char s[32];
	scanf("%d",&n);
	for(i = 1;i <= n;i++){
		for(j = 1;j <= n;j++){
			scanf("%s",s);
			if(i == j){continue;}
			c = strcmp("nyanpass",s);
			if(c != 0){r[j]=1;}
		}
	}
	for(i = 1;i <= n;i++){
		if(!(r[i])){
			if(zr){printf("-1\n");return 0;}else{zr = i;}
		}
	}
	if(zr){printf("%d\n",zr);}else{printf("-1\n");}
	return 0;
}