N = int(input())
L = [input().split() for _ in range(N)]
C = [list(i) for i in zip(*L)]

c = []
for i, j in enumerate(C):
    x = set(j)
    if len(x) == 2 and 'nyanpass' in x:
        c.append(i+1)

print([-1, *c][len(c) == 1])