#include <cstdio>
using namespace std;
int v[10005], c[10005], cost[10005];
int rucsac(int n, int s){
    int max = 0, i, j, min = 50000;
    for (i = 1; i <= 10005; i ++)
        cost[i] = 50000;
    for (i = 1; i <= n; i ++){
        for (j = max; j >= 0; j --){
            if (cost[j] + c[i] < cost[j + v[i]])
                cost[j + v[i]] = cost[j] + c[i];
            if (max < j + v[i] && j + v[i] < s)
                max = j + v[i];
            else if (j + v[i] >= s && cost[j + v[i]] < min)
                min = cost[j + v[i]];
        }
    }
    return min;
}
int main(){
    freopen("energii.in", "r", stdin);
    freopen("energii.out", "w", stdout);
    int n, s, i, x;
    scanf("%d%d", &n, &s);
    for (i = 1; i <= n; i ++)
        scanf("%d%d", &v[i], &c[i]);
    x = rucsac(n, s);
    if (x == 50000)
        x = -1;
    printf("%d\n", x);
    return 0;
}