#include<stdio.h>
#define N 200001
typedef struct stack
{long st[N],sp;};
long n,m,a1[N],a2[N],c[N],k,i,t;

void push(stack &s,long x)
{s.st[++s.sp]=x;}

long pop(stack &s)
{return s.st[s.sp--];}

void dfs(long v)
{long x,y;
stack s;
s.sp=0;
push(s,v);
while(s.sp!=0)
        {x=pop(s);
        c[x]=1;
        for(k=1;k<=m;k++)
        if(a1[k]==x&&c[a2[k]]==0)
               {c[a2[k]]=1;
               push(s,a2[k]);}}}

int main()
{freopen("dfs.in","r",stdin);
freopen("dfs.out","w",stdout);
scanf("%ld%ld",&n,&m);
for(k=1;k<=m;k++)
       scanf("%ld%ld",&a1[k],&a2[k]);
for(i=1;i<=n;i++)
       c[i]=0;
t=0;
for(i=1;i<=n;i++)
if(c[i]==0)
       {t++;
       dfs(i);}
printf("%ld\n",t);
fclose(stdin);
fclose(stdout);
return 0;}