n=int(input())
array=[[1 if i in ("nyanpass","-") else 0 for i in input().split(" ") ] for _ in range(n)]
nyan=[1 if sum([e[i] for e in array])==n else 0 for i in range(n)]
if sum(nyan)>1 or sum(nyan)==0:print(-1)
else:print(nyan.index(1)+1)