import std.stdio;
import std.algorithm;
import std.string;
import std.range;
import std.array;
import std.conv;
import std.complex;
import std.math;
import std.ascii;
import std.bigint;
import std.container;
import std.typecons;

auto readInts() {
	return array(map!(to!int)(readln().strip().split()));
}
auto readInt() {
	return readInts()[0];
}
auto readLongs() {
	return array(map!(to!long)(readln().strip().split()));
}
auto readLong() {
	return readLongs()[0];
}

void readlnTo(T...)(ref T t) {
    auto s = readln().split();
    assert(s.length == t.length);
    foreach(ref ti; t) {
        ti = s[0].to!(typeof(ti));
        s = s[1..$];
    }
}

const real eps = 1e-10;

void main(){
    long n, m;
    readlnTo(n, m);
    auto red = new bool[](n+1);
    auto num = new int[](n+1);
    red[1] = true;
    num[] = 1;
    foreach(i; iota(m)) {
        long x, y;
        readlnTo(x, y);
        if(red[x]) {
            red[y] = true;
        }
        num[y] += 1;
        num[x] -= 1;
        if(num[x] == 0) {
            red[x] = false;
        }
    }
    writeln(red.filter!(a => a).count);
}

