// dfmt off
T lread(T=long)(){return readln.chomp.to!T;}T[] lreads(T=long)(long n){return iota(n).map!((_)=>lread!T).array;}
T[] aryread(T=long)(){return readln.split.to!(T[]);}void arywrite(T)(T a){a.map!text.join(' ').writeln;}
void scan(L...)(ref L A){auto l=readln.split;foreach(i,T;L){A[i]=l[i].to!T;}}alias sread=()=>readln.chomp();
void dprint(L...)(lazy L A){debug{auto l=new string[](L.length);static foreach(i,a;A)l[i]=a.text;arywrite(l);}}
static immutable MOD=10^^9+7;alias PQueue(T,alias l="b<a")=BinaryHeap!(Array!T,l);import std;
// dfmt on

void main()
{
    long N, M;
    scan(N, M);
    auto ans = new bool[](N);
    ans[0] = true;
    auto cnt = new long[](N);
    cnt[] = 1;
    foreach (_; 0 .. M)
    {
        long x, y;
        scan(x, y);
        x--, y--;
        ans[y] = ans[y] || ans[x];
        cnt[y]++;
        cnt[x]--;
        if (cnt[x] == 0)
            ans[x] = false;
    }
    ans.sum().writeln();
}
