#include <fstream>
#include <iostream>
using namespace std;
 
#define inf 1<<30
 
ifstream fi("energii.in");
ofstream fo("energii.out");
 
int a[100000],i,j,c,p,g,w;
 
int main(){
     
    fi >> g >> w;
    for (i=1; i<=w+10001; i++) a[i]=inf;
 
    for (i=1; i<=g; i++){
        fi >> p >> c;
        for (j=w; j>=0; j--)
            if (a[j]+c<a[j+p]) a[j+p]=a[j]+c;
    }
 
    c=inf;
    for (i=w; i<=w+10001; i++) if (a[i]<c) c=a[i];
     
    if (c==inf) fo << "-1"; else fo << c;
     
    return 0;
}