#include <fstream>
#define INF (1<<30)
#define min(a,b) ((a<b) ? a : b)
using namespace std;
ifstream fin("energii.in");
ofstream gout("energii.out");
int d[1001][5001],e[1001],c[1001];
int main()
{
    int n,g,i,j;
    fin>>n>>g;
    for(i=1;i<=n;i++)
        fin>>e[i]>>c[i];

    for(i=0;i<=n;i++)
        for(j=1;j<=g;j++) d[i][j]=INF;

    for(i=1;i<=n;i++)
        for(j=1;j<=g;j++)
        {
            if(e[i]<=j) d[i][j]=min(d[i-1][j],d[i-1][j-e[i]]+c[i]);
            else d[i][j]=min(d[i-1][j],c[i]);
        }

    if(d[n][g]==INF) gout<<-1;
    else gout<<d[n][g];
}