#include <cstdlib>
#include <cstdio>
#include <limits>
#include <iostream>
 
using namespace std;
 
#define MAXW 5007
int minimum[MAXW];
int updated[MAXW];
 
int main()
{
    FILE* f = fopen("energii.in", "r");
    FILE* g = fopen("energii.out", "w");
    int n, total, eg[1002], cg[1002];
    for (int i = 0; i < MAXW; ++i) {
        minimum[i] = numeric_limits<int>::max();
    }
    fscanf(f, "%d", &n);
    fscanf(f, "%d", &total);
    for (int i = 0; i < n; ++i)
    {
        fscanf(f, "%d %d", &eg[i], &cg[i]);
    }
    minimum[0] = 0;
    for (int i = 0; i < n; ++i)
    {
        for (int j = total; j >= 0; --j)
        {
            if (minimum[j] != numeric_limits<int>::max()) {
                minimum[j + eg[i]] = min(minimum[j + eg[i]], minimum[j] + cg[i]);
            }
        }
    }
 
    int minmin = numeric_limits<int>::max();
    for (int i = total; i < MAXW; i++) {
        if (minmin > minimum[i]) {
            minmin = minimum[i];
        }
    }
 
    if (minmin == numeric_limits<int>::max()) {
        fprintf(g, "%d\n", -1);
    } else {
        fprintf(g, "%d\n", minmin);
    }
 
    return 0;
}