package main

import (
	"fmt"
)


func main() {
	var N int
	fmt.Scan(&N)
	a := make([]int, N)
	for i := 0; i<N; i++ {
		for j := 0; j<N; j++ {
			var nyan string
			fmt.Scan(&nyan)
			if i==j {
				continue
			}
			if nyan!="nyanpass" {
				a[j] = 1
			}
		}
	}
	ans := 0
	for i := 0; i<N; i++ {
		if a[i] == 0{
			if ans == 0{
				ans = i+1
			}else{
				ans = -1
			}
		}
	}
	if ans <= 0 {
		fmt.Println("-1")
	}else {
		fmt.Println(ans)
	}
}