Problem:
Problem Statement

We have N boxes, numbered 1 through N. At first, box 1 contains one red ball, and each of the other boxes contains one white ball.

Snuke will perform the following M operations, one by one. In the i-th operation, he randomly picks one ball from box x_i, then he puts it into box y_i.

Find the number of boxes that may contain the red ball after all operations are performed.

Constraints

2≤N≤10^5

1≤M≤10^5

1≤x_i,y_i≤N

x_i≠y_i

Just before the i-th operation is performed, box x_i contains at least 1 ball.

Input

The input is given from Standard Input in the following format:

N M
x_1 y_1
:
x_M y_M

Output

Print the number of boxes that may contain the red ball after all operations are performed.

Sample Input 1

3 2
1 2
2 3

Sample Output 1

2

Just after the first operation, box 1 is empty, box 2 contains one red ball and one white ball, and box 3 contains one white ball.

Now, consider the second operation. If Snuke picks the red ball from box 2, the red ball will go into box 3. If he picks the white ball instead, the red ball will stay in box 2.
Thus, the number of boxes that may contain the red ball after all operations, is 2.

Sample Input 2

3 3
1 2
2 3
2 3

Sample Output 2

1

All balls will go into box 3.

Sample Input 3

4 4
1 2
2 3
4 1
3 4

Sample Output 3

3

Solution in PyPy3 (2.4.0) (judge verdict: Runtime Error)

    import sys, re, os
    from collections import deque, defaultdict, Counter
    from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians
    from itertools import permutations, combinations, product, accumulate
    from operator import itemgetter, mul
    from copy import deepcopy
    from string import ascii_lowercase, ascii_uppercase, digits
    from fractions import gcd
    def input(): return sys.stdin.readline().strip()
    def STR(): return input()
    def INT(): return int(input())
    def MAP(): return map(int, input().split())
    def S_MAP(): return map(str, input().split())
    def LIST(): return list(map(int, input().split()))
    def S_LIST(): return list(map(str, input().split()))
    sys.setrecursionlimit(10 ** 9)
    inf = sys.maxsize
    mod = 10 ** 9 + 7
     
    n, m = MAP()
    red = [False for _ in range(n)]
    bal = [1 for _ in range(n)]
    red[0] = 1
    for i in range(m):
        x, y = MAP()
        if red[x - 1]:
            red[y - 1] = True
            if bal[x - 1] == 1:
                red[x - 1] = False
        bal[x - 1] -= 1
        bal[y - 1] += 1
    print(sum(red))