#pragma GCC optimize("Ofast")

#include<bits/stdc++.h>

#define all(s) s.begin(),s.end()
#define rc(x) return cout<<x,0
#define rcc(s) cout<<s,exit(0)
#define forn(i,n) for(int i=0;i<int(n);i++)
#define pb push_back
#define mp make_pair
#define fr first
#define sc second

typedef long long ll;
typedef long double ld;

const int nmax=15e3+3;
const int mod=998244353;
const ll inf=2e9+3;

using namespace std;

int dp[nmax];

int main()
{
  freopen("energii.in","r",stdin);
  freopen("energii.out","w",stdout);
  //mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
	ios_base::sync_with_stdio(false);cin.tie(0);cerr.tie(0);cout.tie(0);
  int n,k;
  cin>>n>>k;
  int sol=inf;
  for(int i=1;i<=k;i++) dp[i]=inf;
  for(int i=1;i<=n;i++)
  {
    int a,b;
    cin>>a>>b;
    for(int j=k;j>=0;j--)
    {
      if(dp[j]!=inf && j+a<=k)
      {
        dp[j+a]=min(dp[j]+b,dp[j+a]);
      } else
      if(dp[j]!=inf && j+a>k)
      {
        dp[k]=min(dp[k],dp[j]+b);
      }
    }
  }
  if(dp[k]==inf) cout<<-1; else cout<<dp[k];
}