//Daniel RULZZ B|

#include <fstream>
#include <iostream>
#define Inf  1234567890
using namespace std;
int v[5006003];
int main()
 {
  ifstream f("energii.in");
  ofstream g("energii.out");

  int n,s, min = Inf, i,j,a,b;

  f>>n>>s;

  for(i=1;i<=20100;++i)
   v[i] = Inf;

  for(i=1;i<=n;++i)
   {
    f>>a>>b;

    for(j=10010;j>=0;--j)
     if(v[j] != Inf)
      {
       if(v[j+a] >= v[j] + b)
        v[j+a] = v[j] + b;

       if(v[j+a] < min && (j+a) >= s)
        min = v[j+a];
      }
   }

  if(min != Inf)
   g<<min;
    else g<<-1;

  return 0;
 }