#include <cstdio>
#include <cmath>
#include <vector>
#include <algorithm>
#include <cassert>
#include <cstring>
#include <climits>
#include <set>
#include <map>
#include <ctime>
#include <functional>
using namespace std;
typedef long long LL;

#ifdef INFOARENA
#define ProblemName "energii"
#endif

#define MCONCAT(A, B) A B
#ifdef ProblemName
#define InFile MCONCAT(ProblemName, ".in")
#define OuFile MCONCAT(ProblemName, ".out")
#else
#define InFile "fis.in"
#define OuFile "fis.out"
#endif

#define MAXN 1100
#define MAXW 10010

int phys[2][MAXW];
int *prv = &phys[0][0], *cur = &phys[1][0];
int N, tar;
#define cost second
#define energy first

pair<int, int> v[MAXN];

int DP() {
	memset(phys, 0xFF, sizeof(phys));
	prv[0] = 0;
	for (int i = 0; i < N; ++i)
	for (int j = 0; j < MAXW; ++j) {
		cur[j] = prv[j];
		if (j < v[i].energy) continue;
		if (prv[j - v[i].energy] < 0) continue;
		int cand = prv[j - v[i].energy] + v[i].cost;
		if (cur[j] < 0 || cand < cur[j])
			cur[j] = cand;
		swap(cur, prv);
	}
	int best = INT_MAX;
	for (int i = tar; i < MAXW; ++i)
	if (prv[i] >= 0)
		best = min(best, prv[i]);
	return (best == INT_MAX) ? (-1) : best;
}

int main() {
	assert(freopen(InFile, "r", stdin));
	assert(freopen(OuFile, "w", stdout));
	scanf("%d%d", &N, &tar);
	for (int i = 0; i < N; ++i)
		scanf("%d%d", &v[i].energy, &v[i].cost);
	sort(v, v + N);
	printf("%d\n", DP());
	return 0;
}