#include <iostream>
#include <fstream>
#include <algorithm>

using namespace std;

ifstream in("energii.in");
ofstream out("energii.out");

const int N = 5002;
const long long M = 10002;
int n, total_amount;
long long dp[M][M], amount[N], cost[N];

int main() {
	in >> n >> total_amount;
	for (int i = 1; i <= n; i++) 
		in >> amount[i] >> cost[i];
	
	int l = 0;
	for (int i = 0; i <= n; i++)
		for (int j = 0; j <= total_amount; j++)
			dp[i][j] = 10002;
	for (int i = 1; i <= n; i++, l = 1 - l) {
		for (int j = 0; j <= total_amount; j++) {
			if (amount[i] < j) dp[1 - l][j] = min(dp[1 - l][j], dp[l][j - amount[i]] + cost[i]);
			else
				dp[1 - l][j] = min(dp[l][j], cost[i]);
		}
	}
	out << dp[l][total_amount];
	return 0;
} 

/*#include <iostream>
#include <algorithm>

using namespace std;

struct object {
	int value, weight;
}v[1001];

bool cmp(const object& x, const object& y) {
	return (x.value * y.weight > y.value* x.weight);
}

int main() {
	int maximumWeight, n;
	cin >> n >> maximumWeight;
	for (int i = 1; i <= n; i++) {
		cin >> v[i].weight >> v[i].value;
	}
	sort(v + 1, v + n + 1, cmp);

	for (int i = 1; i <= n; i++)
		cout << v[i].weight << ' ' << v[i].value << "; ";
	cout << endl;

	int i = 0;
	double sum = 0;
	while (i <= n && maximumWeight > 0) {
		if (v[i].weight <= maximumWeight) {
			sum += v[i].value;
			maximumWeight -= v[i].weight;
		}
		else {
			sum += (double)maximumWeight / v[i].weight * v[i].value;
			maximumWeight = 0;
		}
		i++;
	}
	cout << sum;
	return 0;
}*/