package main

import (
	"fmt"
)

const nyanpass = "nyanpass"

func main() {
	var N int
	fmt.Scanln(&N)
	ns := make([]bool, N)
	var say string
	for i := 0; i < N; i++ {
		for j := 0; j < N; j++ {
			fmt.Scan(&say)
			if i == j {
				continue
			}
			if say != nyanpass {
				ns[j] = true
			}
		}
	}
	s := make([]int, 0, N)
	for i := range ns {
		if !ns[i] {
			s = append(s, i)
		}
	}
	if len(s) != 1 {
		fmt.Println(-1)
		return
	}
	fmt.Println(s[0] + 1)
}