n = int(input())
matrix = []
for _ in range(n):
    row = input().split()
    matrix.append(row)

candidates = []

for k in range(1, n + 1):
    # Check condition 1: all i (i != k) must have A[i][k] == "nyanpass"
    valid = True
    for i in range(1, n + 1):
        if i == k:
            continue
        if matrix[i-1][k-1] != 'nyanpass':
            valid = False
            break
    if not valid:
        continue
    
    # Check condition 2: all j != k must not be candidates
    for j in range(1, n + 1):
        if j == k:
            continue
        all_nyan = True
        for m in range(1, n + 1):
            if m == j:
                continue
            if matrix[m-1][j-1] != 'nyanpass':
                all_nyan = False
                break
        if all_nyan:
            valid = False
            break
    if valid:
        candidates.append(k)

if len(candidates) == 1:
    print(candidates[0])
else:
    print(-1)