#include <bits/stdc++.h>

using namespace std;

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

int main(){
    int n,tg;
    fin>>n>>tg;
    vector<int>dp(1000000,INT_MAX-100);
    vector<pair<int,int>>v(n);
    for(auto &x:v){
        fin>>x.first>>x.second;
    }
    dp[0]=0;
    int out=INT_MAX-1;
    for(int i=0;i<n;i++){
        for(int j=tg;j>=v[i].first;j--){
            dp[j]=min(dp[j],dp[j-v[i].first]+v[i].second);
        }
    }
    int rez=INT_MAX-1;
    for(int i=1;i<=10000;i++){
        if(i>=tg)rez=min(rez,dp[i]);
    }
    if(rez!=INT_MAX-1)fout<<rez;
    else fout<<"-1";
    return 0;
}