S = 'nyanpass'

N = int(input())

ans = [0] * N

for i in range(N):
    
    A = input().split()
    
    for j in range(N):
        
        if A[j] == S:
            
            ans[j] += 1
    
if ans.count(N - 1) == 1:
    
    print(ans.index(N - 1) + 1)
    
else:
    
    print(-1)