#include <iostream>
#include <fstream>

int min(int a, int b)
{
	return a > b ? b : a;
}
int max(int a, int b)
{
	return a > b ? a : b;
}
using namespace std;

int main()
{
	int G, W, EG, CG, i, j, D[100][100];

	freopen("energii.in", "r", stdin);
	freopen("energii.out", "r", stdout);

	cin>>G>>W;

	for(i=1;i<=G;++i)
		for(j=0;j<=W;++j)
			D[i][j] = 99999;

	for(i=1;i<=G;++i)
	{
		cin>>EG>>CG;
		
		for(j=0;j<=W;++j)
		{

			if(j < EG[i])
				D[i][j] = D[i-1][j];
			else
				D[i][j] = min(D[i][j], CG[i] + D[i-1][j - EG[i]]);
		
		}
	}
	
	cout<<D[G][W]<<"\n";

	return 0;
	
}