#include <bits/stdc++.h>

#define WMAX 5001
#define INF 0x3f3f3f3f
int dp[WMAX];

int main() {
	freopen("energii.in", "r", stdin);
	freopen("energii.out", "w", stdout);

	int n, g, w, p;
	scanf("%d", &n);
	scanf("%d", &g);
	int power[n + 1], costs[n + 1];
	memset(dp, INF, sizeof(dp));

	for (int i = 1 ; i <= n ; ++i) {
		scanf("%d%d", &power[i], &costs[i]);
	}

	for (int i = 1 ; i <= n ; ++i) {
		for (int j = g ; j >= power[i] ; --j) {
			dp[j] = std::min(dp[j], dp[j - power[i]] + costs[i]);
		}

		for (int j = 1 ; j < power[i] ; ++j) {
			dp[j] = std::min(dp[j], costs[i]);
		}
	}

	dp[g - 1] == INF ? printf("-1") : printf("%d\n", dp[g - 1]);
	return 0;
}