#include <stdlib.h>
#include <stdio.h>
#define MAX 11000
#define INF 9999999
int P,C;
int p1,p2;

int elCon[MAX];
int mark[MAX];
int cnt;

void swp(int *a, int *b){
    int pom;
    if (*b<*a){
	pom=*a;
	*a=*b;
	*b=pom;
    }
}

int main(void){
  int i,j,k,n;
 
  scanf("%d %d\n",&P, &C);
  for(;;){
      if(P==0 && C==0) break;
      for (i=0;i<MAX;i++){
        elCon[i]=i;
      }
      cnt=0;
      while(C--){
        scanf("%d %d\n",&p1,&p2);
	swp(&p1,&p2);
	elCon[p2]=p1;
      }
      for(i=0;i<P;i++){
        if(elCon[i]==i) cnt++;
      }
      printf("%d\n", cnt);
      scanf("%d %d\n",&P, &C);
  }
  return 0;
}