def main():
    n = int(input())
    s = "nyanpass"
    l = [False]*n
    for i in range(n):
        a = input().split()
        for j in range(n):
            l[j] = max(a[j] != s and a[j] != "-", l[j])
    ans = []
    # print(l)
    for i in range(len(l)):
        if not l[i]:
            ans.append(i)
    # print(ans)
    if len(ans) == 1:
        print(ans[0]+1)
    else:
        print(-1)

    pass


if __name__ == "__main__":
    main()