#include <fstream>
#define oo (1<<26)
using namespace std;
ifstream in ("energii.in");
ofstream out("energii.out");
int n, p, v[1005], g[1005], a[1005][5005];
int main(){
    in>>n>>p;
    for(int i=1; i<=n;++i) in>>v[i]>>g[i];
    for(int j=0;j<=p;++j) a[0][j]=oo;
    for(int i=0;i<=n;++i) a[i][0]=oo;
    for(int i=1;i<=n;++i){
        for(int j=1;j<=p;++j){
            if(j>v[i])
                a[i][j]=min(a[i - 1][j],a[i - 1][j - v[i]]+g[i]);
            else
                a[i][j]=min(a[i - 1][j], g[i]);
        }
    }
    if(a[n][p]!=oo) out<<a[n][p]<<'\n';
    else out<<"-1\n";
}