// 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, core.bitop;
// dfmt on

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