def nyan(N: int, array):
    nyan = []
    for i in range(N):
        for j in range(N):
            if array[i][j] == "nyanpass":
                if not j+1 in nyan:
                    nyan.append(j+1)
            else:
                if j+1 in array:
                    nyan.remove(j+1)
    if len(nyan) == 1:
        return nyan[0]
    else:
        return -1
        
N = int(input())
array = zip(*(input().split() for __ in range(N)))
nyan(N, array)