import core.bitop;
import std.algorithm;
import std.ascii;
import std.bigint;
import std.conv;
import std.functional;
import std.math;
import std.numeric;
import std.range;
import std.stdio;
import std.string;
import std.random;
import std.typecons;
import std.container;

alias sread = () => readln.chomp();
ulong MOD = 1_000_000_007;
ulong INF = 1_000_000_000_000;
ulong MIDDLE = 100_000;
alias Pair = Tuple!(long, "flag", long, "num");

T lread(T = long)()
{
    return readln.chomp.to!T();
}

T[] aryread(T = long)()
{
    return readln.split.to!(T[])();
}

void scan(TList...)(ref TList Args)
{
    auto line = readln.split();
    foreach (i, T; TList)
    {
        T val = line[i].to!(T);
        Args[i] = val;
    }
}

void main()
{
    long n, m;
    scan(n, m);
    auto box = new long[](n);
    auto red = new long[](n);
    box[] = 1;
    red[0] = 1;
    foreach(i; iota(m))
    {
        long x, y;
        scan(x, y);
        x--, y--;
        if(box[x])
        {
            box[x]--, box[y]++;
            red[y]++;
            if(!box[x])
                red[x]--;
        }
    }
    red.sum.writeln();
}
