#include <stdio.h>
#include <stdlib.h>

typedef struct station{

	int input;
	int output;	

} station;

typedef struct pipe {
	int from;
	int to;

} pipe;

int main(){

	int st, pipes;

	scanf("%d %d", &st, &pipes);
	station* tomb = (station*) malloc(st * sizeof(station));
	pipe* tomb2 = (pipe*) malloc(pipes * sizeof(pipe));

	int i1, i2;
	int begin = -1, end = -2;

	int i;

	for (i = 0; i < pipes; i++){

		scanf("%d %d", &i1, &i2);
		tomb[i1-1].output++;
		tomb[i2-1].input++;
		
		tomb2[i].from = i1;
		tomb2[i].to = i2;
	

	}

	int count = 0;

	for (i = 0; i < st; i++){
	

		if ((tomb[i].input != 0) && (tomb[i].output != 0)){
			
			count += tomb[i].input - 1;			
		}

		else if (tomb[i].input == 0) {
		
			begin = i + 1;				
		}

		else if (tomb[i].output == 0){
				
			end = i + 1;
		}

	}

	for (i = 0; i < pipes; i++){

		if (tomb2[i].from == begin && tomb2[i].to == end){
			count++;
		}

	}

	printf("%d\n", count);

	return 0;

}