#include <fstream>
#include <algorithm>
#include <iostream>
using namespace std;
int n,e,energie[1001],cost[1001],x[2][5001];
ifstream f("energii.in");
ofstream g("energii.out");
int main(){
    f>>n>>e;
    for(int i=0;i<=1;++i){
        for(int j=1;j<=e;j++)
            x[i][j]=-1;
    }

    for(int i=1;i<=n;++i){
        f>>energie[i];
        f>>cost[i];
    }
    int ln=0;
    long long int s=0;
    for(int i=1;i<=n;++i, ln=1-ln){
       s+=energie[i];
       for(int j=1;j<=e;++j){
            x[ln][j]=x[1-ln][j];
            if(j<=energie[i]){
                if(x[ln][j]==-1)
                    x[ln][j]=cost[i];
                else
                    x[ln][j]=min(x[ln][j],cost[i]);
            }
            else if(s>j){
                if(x[ln][j]==-1)
                    x[ln][j]=x[1-ln][j-energie[i]]+cost[i];
                else
                    x[ln][j]=min(x[ln][j],x[1-ln][j-energie[i]]+cost[i]);
            }
            else
                break;
       }
    }
    if(x[1-ln][e]!=0)
        g<<x[1-ln][e];
    else
        g<<-1;
    return 0;
}