#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=1000010;
ll n,m,a[N],b[N],ans;
int main () {
    freopen("Mining.in","r",stdin);
    freopen("Mining.out","w",stdout);
    ios::sync_with_stdio(0);
    cin.tie(0),cout.tie(0);
    cin >> n >> m;
    for (int i=1;i<=n;i++) {
        cin >> a[i] >> b[i];
    }
    sort(a+1,a+1+n);
    for (int i=n;i>=1;i--) {
        if (m-b[1]>=0) {
            m-=b[1];
            ans+=a[i];
        }
    }
    cout << ans <<endl;
    return 0;
}