#include <bits/stdc++.h>

using namespace std;

int d[10005];

int main()
{
    freopen("energii.in", "r", stdin);
    freopen("energii.out", "w", stdout);
    int n, a, x, y, ans = -1;
    scanf("%d%d", &n, &a);
    d[0] = 0;
    for(int i = 1; i < a; i++) d[i] = -1;
    for(int i = 1; i <= n; i++)
    {
        scanf("%d%d", &x, &y);
        for(int i = a - 1; i >= 0; i--)
            if(d[i] != -1 and i + x >= a)
                ans = (ans == -1 ? d[i] + y : min(ans, d[i] + y));
            else if(d[i] != -1)
                d[i + x] = (d[i + x] == -1 ? d[i] + y : min(d[i] + y, d[i + x]));
    }
    printf("%d", ans);
    return 0;
}