N = int(input())
A = []
B = []
for i in range(N) :
    L = list(map(str,input().split()))
    for j in range(N) :
        if L[j] == "nyanpass" :
            A.append(j+1)
if len(A) == 0 :
    print(-1)
else :    
    for k in range(N) :
        a = A.count(k+1)
        if a == N-1 :
            B.append(k+1)
    if len(B) >= 2 :
        print(-1)
    else :
        print(B[0])