ll@n,@m,u[m],v[],w[n+1]{},s[n+1]{},t[n+1]{},z=-1;
rd((u,v)(m));
unionFind f('m',n+1,1);
rep(i,m){
	f(u[i],v[i]);
	w[u[i]]+=1;
	w[v[i]]-=1;
	s[u[i]]=1;
	s[v[i]]=1;
}
rep(j,1,n+1){
	if(w[j]>0){
		t[f(j)]+=w[j];
	}
}
rep(j,1,n+1){
	if(j==f(j)){
		z+=max(s[j],t[j]);
	}
}
wt(z);