N = int(input())
A = []
B = []
for i in range(N) :
    greeting = list(map(str,input().split()))
    for j in range(N) :
        if greeting[j] == "nyanpass" :
            A.append(j+1)
if len(A) == 0 :
    print(-1)
else :
    for k in range(len(A)) :
        b = A.count(k)
        B.append(b)
    if len(B) == 1 :
        print(B[0])
    else :
        print(-1)