N = input()
inp = []
mat = [["-" for i in range(0, N)] for j in range(0, N)]
for i in range(0,N):
    inp = raw_input().split()
    for j in range(0, N):
        if inp[j] != "nyanpass":
            mat[i][j] = 0
        else:
            mat[i][j] = 1
out = [0 for i in range(0, N)]
for i in range(0, N):
    for j in range(0, N):
        out[i] += mat[j][i]
if out.count(N-1) == 1:
    print out.index(N-1)+1
else:
    print -1