#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[10002], cg[10002];
	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]);
	}
	for (int i = 0; i < n; ++i)
	{
		for (int j = MAXW; j > 0; --j)
		{
			if (minimum[j] != numeric_limits<int>::max()) {
				minimum[j + eg[i]] = min(minimum[j + eg[i]], minimum[j] + cg[i]);
			}
		}
		if (minimum[eg[i]] > cg[i]) {
			minimum[eg[i]] = 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", -1);
	} else {
		fprintf(g, "%d", minmin);
	}

	return 0;
}