package main

import "fmt"

func main() {
	var N int
	fmt.Scan(&N)
	A := make([][]string, N)
	r := make([]int, 0)
	for i := range A {
		A[i] = make([]string, N)
		for j := range A[i] {
			fmt.Scan(&A[i][j])
		}
	}
	// fmt.Println("N", N, "A", A)
	for j := 0; j < N; j++ {
		ok := true
		for i := 0; i < N; i++ {
			if A[i][j] != "-" && A[i][j] != "nyanpass" {
				ok = false
			}
		}
		if ok {
			r = append(r, j+1)
		}
	}
	if len(r) == 1 {
		fmt.Println(r[0])
	} else {
		fmt.Println(-1)
	}
}