#include <fstream>
#include <cstring>

using namespace std;

#define Nmax 10001
#define Mmax 100001
#define inf (1<<28)

int N, W, S, minim = inf;
int E[Nmax], C[Nmax], cost[Mmax];

ifstream f("energii.in");
ofstream g("energii.out");

void citire(){

    f >> N >> W;

    for( int i = 1; i <= N; i++ ) {

        f >> E[i] >> C[i];
        S += E[i];
    }

    for ( int i = 1; i <= 20000; i++)
        cost[i] = inf;
}

void knapsack (){

    for( int i = 1; i <= N; i++ ) {
        for( int j = W; j >= 0; j-- ){

            if ( cost[j] != inf )

                if ( cost[j] + C[i] < cost[ j + E[i] ] )
                    cost[ j + E[i] ] = cost[j] + C[i];

        }
    }

    for( int i = W; i <= 20000; i++ )
        minim = min( cost[i], minim );
}

void rezolva(){

    if ( S < W )
        g << "-1\n";

    else {
            knapsack();
            g << minim << "\n";
         }
}

int main(){

    citire();
    rezolva();

    return 0;
}