#include <bits/stdc++.h>
using namespace std;
int e[1001], c[1001], x[20001];
int main()
{
    ifstream in("energii.in");
    ofstream out("energii.out");
    int i, j, n, m;
    in >> n >> m;
    for(i = 1;i <= n;i++){
        in >> e[i] >> c[i];
        e[i] = min(e[i], m);
    }
    for(i = 1;i <= 10000;i++)
        x[i] = 1000000000;
    for(i = 1;i <= n;i++)
        for(j = e[i];j <= 20000;j++)
            x[j] = min(x[j], x[j - e[i]] + c[i]);
    out << x[m];
}