#include <bits/stdc++.h>
using namespace std;

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

#define cin fin
#define cout fout

int n, gmax;
vector<int> dp(5001, INT_MAX);
int w[1001],v[1001];
int main() {

    cin >> n >> gmax;
    for(int i = 1; i <= n; i++) {
        cin >> w[i] >> v[i];
    }
    dp[0]=0;
    for(int i = 1; i <= n; i++) {
        for(int j = w[i]; j <= gmax; j++) {
            dp[j]=min(dp[j], dp[j-w[i]]+v[i]);
        }
    }
    if (dp[gmax]==INT_MAX) {
        cout << -1;
    } else {
        cout << dp[gmax];
    }
    return 0;
}