n = int(input())
a = [input().split() for i in range(n)]
candidate = []
for i in range(n):
    for j in range(n):
        if i == j:
            continue
        if a[j][i] != "nyanpass":
            break
    else:
        candidate.append(i)
if len(candidate) == 1:
    print(candidate[0] + 1)
else:
    print(-1)