#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 = 60000000, a;
bool bn[3][E];

int main () {
    
    fin >> n >> w;
    
    for (i = 1; i <= n; i++)
        fin >> e[i] >> c[i];
    
    x = 1;  y = 2;
    
    for (i = 1; i <= n; i++)
    {
        for (j = 1; j <= w+e[i]; j++)
        {
            if (bn[x][j] == 1)
            {
                enrg[y][j] = enrg[x][j];
                bn[y][j] = 1;
            }
            
            if ((bn[x][j-e[i]] == 1 || j <= e[i]) && (bn[y][j] == 0 || enrg[y][j] > enrg[x][j-e[i]]+c[i]))
            {
                enrg[y][j] = enrg[x][j-e[i]]+c[i];
                bn[y][j] = 1;
            }
            
            if (j >= w && enrg[y][j] < sol && bn[y][j] == 1)
                sol = enrg[y][j];
            
            bn[x][j-e[i]] = 0;
        }
        
        if (c[i] < enrg[y][e[i]] || bn[y][e[i]] == 0)
        {
            enrg[y][e[i]] = c[i];
            bn[y][e[i]] = 1;
        }
        
        if (e[i] >= w && c[i] < sol)
            sol = c[i];
        
        a = x;
        x = y;
        y = a;
    }
    
    if (sol != 60000000)   fout << sol << "\n";
    else    fout << -1 << "\n";
}