#include <iostream>
#include <vector>

using namespace std;

const int MAXG=1001;

const int MAXW=5001;

int e[MAXG], c[MAXG];

vector<int> previous(MAXW);

vector<int> curr(MAXW);

int main()
{
    freopen("energii.in", "r", stdin);
    freopen("energii.out", "w", stdout);
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int g,w;
    cin>>g>>w;
    for (int i=0;i<g;i++){
        cin>>e[i]>>c[i];
    }
    for (int i=1;i<=g;i++){
        for (int j=0;j<=w;j++){
            if (j-e[i]>=0){
                curr[j]=max(previous[j], previous[j-e[i]]+c[i]);
            }
        }
        previous=curr;
    }
    if (curr[w]){
        cout<<curr[w];
    }
    else{
        cout<<-1;
    }
    return 0;
}