N = int(input())
g = [set() for i in range(N)]
for i in range(N):
    for j, s in enumerate(input().split(' ')):
        if i == j: continue
        g[j].add(s)
n = []
for ii, c in enumerate(g):
    if c == {'nyanpass'}:
        n.append(ii)
if len(n) == 1:
    print(n[0]+1)
else:
    print(-1)