#include <iostream>
#include <fstream>
#define E 20003
#define dim 1003

using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");

int n, i, j, w, e[dim], c[dim], enrg[3][E], x, y, sol, a;

int main () {
    
    fin >> n >> w;
    
    for (i = 1; i <= n; i++)
        fin >> e[i] >> c[i];
    
    x = 1;  y = 2;
    enrg[1][e[1]] = c[1];
    
    for (i = 2; i <= n; i++)
    {
        for (j = 1; j <= w+e[i]; j++)
        {
            if (enrg[x][j] != 0 && j <= w) enrg[y][j] = enrg[x][j];
            
            if (enrg[x][j-e[i]] != 0 && j > e[i] && (enrg[y][j] == 0 || enrg[y][j] > enrg[x][j-e[i]]+c[i]))
                enrg[y][j] = enrg[x][j-e[i]]+c[i];
            
            if (j >= w && (enrg[y][j] < sol || sol == 0) && enrg[y][j] != 0)
                sol = enrg[y][j];
            
            if (j > w) enrg[y][j] = 0;
        }
        
        if (c[i] < enrg[y][e[i]] || enrg[y][e[i]] == 0)   enrg[y][e[i]] = c[i];
        
        if (e[i] >= w && (c[i] < sol || sol == 0))
            sol = c[i];
        
        a = x;
        x = y;
        y = a;
    }
    
    if (sol != 0)   fout << sol << "\n";
    else fout << -1 << "\n";
}