X = "nyanpass"
N = int(input())
B = set()
C = set()
for i in range(N):
    A = list(map(str, input().split()))
    for j in range(N):
        if i != j:
            if A[j] == X:
                B.add(j)
            else:
                C.add(j)
            
if len(B)==1:
    for x in B:
        if not(x in C):
            print(x+1)
            exit()
print(-1)