n = int(input())
vp = [input().split() for _ in range(n)]
c = {i:0 for i in range(1, n+1)}
for p in vp:
    for idx, g in enumerate(p, 1):
        if g == 'nyanpass':
            c[idx] += 1
    
if list(c.values()).count(n-1) == 1:
    for k, v in c.items():
        if v == n-1:
            print(k)
else:
    print(-1)