import core.bitop, std.bitmanip;
import core.checkedint;
import std.algorithm, std.functional;
import std.array, std.container;
import std.bigint;
import std.conv;
import std.math, std.numeric;
import std.range, std.range.interfaces;
import std.stdio, std.string;
import std.typecons;

void main()
{
    int n, m;
    readf("%s %s", &n, &m);
    readln;

    Tuple!(int, int)[] jobs;
    foreach (_; 0 .. n) {
        int a, b;
        readf("%s %s", &a, &b);
        readln;
        
        jobs ~= tuple(b, a);
    }
    
    jobs.sort().reverse();
    
    debug { jobs.writeln; }
    
    long ans = 0;
    int d = 1;
    foreach (j; jobs) {
        if (d + j[1] - 1 <= m) {
            ans += j[0];
            ++d;
        }
    }
    
    ans.writeln;
}