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 C (Clang 3.8.0) (judge verdict: Wrong Answer)

#include <stdio.h>

//デバッグ
void debug(int matrix[], int max)
{
	int i;
	
	for(i=0; i<max; i++)
		printf("%d ", matrix[i]);
	
	printf("\n");
}

//boxセット
void set_box(int matrix[], int max)
{
	int i;
	
	matrix[0] = 1;
	
	for(i=1; i<max; i++)
		matrix[i] = 0;
}

void set_clone(int clone[], int N)
{
	int i;
	
	for(i=0; i<N; i++){
		clone[i] = 1;
	}
}

int main(void)
{
	int N,M;  //入力
	int box_cnt=0, cnt = 0;
	int x,y;  //入力情報
	int box[100]={0};  //箱配列
	int clone[100]={0};
	int i;
	
	//N,Mの入力
	scanf("%d %d", &N, &M);
	
	set_box(box, N);  //セット
	set_clone(clone, N);
	//debug(box, N);  //デバッグ
	
	//入力と箱の移動
	for(i=1; i<=M; i++){
		scanf("%d %d", &x, &y);  //入力
		
		if(x == y)
			continue;
		
		//添え字
		x -= 1;
		y -= 1;
		
		if(clone[x] == 0)
			continue;
		
		//初期処理
		if(x==0 && cnt==0){  //赤ボールの初期位置
			box[y] = box[x];
			box[x] = 0;
			clone[x]--;  //個数を減らす
			clone[y]++;
			cnt++;
		}
		else if(box[x]==1 && box[y]==0){  //1 -> 0 に移動
			box[y] = 1;
			//個数
			clone[y]++;
			clone[x]--;
		}
		else if(box[x]==0 && box[y]==1){  //1 -> 0 に移動
			//個数
			clone[y]++;
			clone[x]--;
		}
		else if(box[x]==0 && box[y]==1){  //1 -> 0 に移動
			//個数
			clone[y]++;
			clone[x]--;
		}
		else if(box[x]==1 && box[y]==1){  //1 -> 1 に移動
			//個数
			clone[y]++;
			clone[x]--;
		}
	}
	
	//出力準備
	for(i=0; i<N; i++){
		if(box[i] == 1 && clone[i] > 0)
			box_cnt++;
	}
	
	printf("%d\n", box_cnt);
	
	return 0;
}