n = int(input())
gl = []
for i in range(n):
    gl.append(input().split())
nyan_ls = []
for i in range(n):
    tl = []
    for j in gl:
        tl.append(j[i])
    tl[i] = "nyanpass"
    if tl.count("nyanpass") == n:
        nyan_ls.append(i + 1)
if len(nyan_ls) == 1:
    print(str(nyan_ls[0]))
else:
    print("-1")