import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
sys.setrecursionlimit(10 ** 7)

n = int(readline())
a = [readline().rstrip().decode().split() for _ in range(n)]
ans = -1
for i in range(n):
    for j in range(n):
        if i == j:
            continue
        if a[j][i] != 'nyanpass':
            break
    else:
        if ans != -1:
            print(-1)
            break
        ans = i + 1
else:
    print(ans)