#include <bits/stdc++.h>
#define DIM 1001
using namespace std;

ifstream fin("energii.in");
ofstream fout("energii.out");

int n, emin, ans, x;
int e[DIM], c[DIM], d[DIM*11];
int i, j;

int main(){
    fin>>n>>emin;
    for(i=1; i<=n; i++)
        fin>>e[i]>>c[i];

    for(i=1; i<=emin; i++)
        d[i]=INT_MAX;

    for(i=1; i<=n; i++){
        for(j=emin-1; j>=0; j--){
            if(d[j]!=INT_MAX){
                x=j+e[i];
                x=min(x, emin);
                d[x]=min(d[x], d[j]+c[i]);
            }
        }
    }
    if(d[emin]==INT_MAX)
        fout<<-1;
    else fout<<d[emin];
}