N = input()
A = []
for i in xrange(N):
    A.append(raw_input().split())
cnt = 0
ans = 0
for i in xrange(N):
    for j in xrange(N):
        if i != j and A[i][j] != "nyanpass":
            break
    else:
        ans = i+1
        cnt += 1
for j in xrange(N):
    for i in xrange(N):
        if i != j and A[i][j] != "nyanpass":
            break
    else:
        ans = j+1
        cnt += 1
if cnt == 1:
    print ans
else:
    print -1