# BOJ - 2458 - 키 순서

Updated:

```
import sys
def solution():
N, M = map(int, sys.stdin.readline().split())
arr = [[0] * N for _ in range(N)]
for _ in range(M):
x, y = map(int, sys.stdin.readline().split())
arr[x-1][y-1] = 1
for k in range(N):
for i in range(N):
for j in range(N):
if (arr[i][k] and arr[k][j]):
arr[i][j] = 1
ret = 0
for i in range(N):
rank = 0
for j in range(N):
rank += arr[i][j] + arr[j][i]
if rank == N - 1:
ret += 1
print(ret)
solution()
```

https://www.acmicpc.net/problem/2458

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