#include <iostream>
#define MAX 1001
#include <limits.h>
#include <fstream>

using namespace std;
int v[MAX],n,g,e,c;

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

int main()
{
    int i,j;
    fin>>n>>g;
    for(i=1;i<=g;++i)
        v[i]=INT_MAX;
    for(i=1;i<=n;++i)
    {fin>>e>>c;
    for(j=g;j>=1;--j)
        if(e>=j)v[j]=min(v[j],c);
    else if(v[j-e]!=INT_MAX)v[j]=min(v[j],v[j-e]+c);

    }

    fout<<(v[g]!=INT_MAX?v[g]:-1);
    return 0;
}