#include <fstream>
#include <climits>
using namespace std;
ifstream cin("energii.in");
ofstream cout("energii.out");
int G,W,i,j,v[1001],c[1001],cmin=INT_MAX,S,g;
int main()
{
    cin>>G>>W;
    for(i=1;i<=G;i++)
        cin>>v[i]>>c[i];
    for(i=1;i<=G;i++){
        S=c[i]; g=v[i];
        for(j=i+1;j<=G;j++)
            if(S+c[j]<W){
                S+=c[j];
                g+=v[j];
        }
        if(S>W)
            cmin=min(cmin,S);
    }
    if(cmin==INT_MAX)
        cout<<-1;
    else
        cout<<cmin;
    return 0;
}