#include <bits/stdc++.h>
using namespace std;
ifstream fin ("rucsac.in");
ofstream fout ("rucsac.out");

struct ceva
{
    int greu,val;
}v[1005];
int n,i,gmax,g;
double q,x;

bool comp(ceva a, ceva b)
{
    return a.val*b.greu>a.greu*b.val;
}
int main()
{
    fin>>n>>gmax;
    for(i=1;i<=n;i++)
        fin>>v[i].greu>>v[i].val;
    sort(v+1,v+n+1,comp);
    i=1;
    while(i<=n)
    {
        if(g+v[i].greu<=gmax)
        {
            g=g+v[i].greu;
            q=q+v[i].val;
            i++;
        }
        else
            if(gmax-g>0)
            {
                x=1.0*(gmax-g)/v[i].greu;
                g=gmax;
                q=q+x*v[i].val;
                i++;
            }
            else
            i=n+1;
    }
    fout<<(int)q;
    return 0;
}