#include <stdio.h>
#include <iostream>
#include <fstream>

using namespace std;

int big[5005];
int c[1001],w[1001];

int main(){

    int n,m,i,j,k;
    
    ifstream  in("energii.in" );
    ofstream out("energii.out");   
    
    in >> n >> m;
    
    for (i=0;i<=m;i++)
      big[i] = -1;
        
    for (i=0;i<n;i++)
      in >> w[i] >> c[i];
    
    big[0] = 0;
      
    for (i=0;i<n;i++)  
      for (j=m;j>=0;j--)
        if (big[j] != -1){
                   
        int rel = j + w[i];
        if (rel > m) rel = m;        
        int val = big[j] + c[i];
        
        if (big[rel] == -1 || (big[rel] > val )) 
          big[rel] = val;
        }   
    
    out << big[m];
                      
    in.close();            
    out.close();    
    
    return 0;
}