#include<fstream>
using namespace std;
int n,gmax,k,c[1001],g[1001],cmax[301],s,i,j;
int main()
{
	ifstream f("energii.in");
	ofstream g1("energii.out");
	f>>n>>gmax;
	for(i=1;i<=n;i++)
	{
		f>>g[i];
		f>>c[i];
	}
	for(i=1;i<=gmax;i++)
		cmax[i]=100000;
	for(s=1;s<=gmax;s++)
		for(i=1;i<=n;i++)
			if(g[i]<=s)
				if(cmax[s]>cmax[s-g[i]]+c[i])
				{
					cmax[s]=cmax[s-g[i]]+c[i];
				}
				
				if(cmax[gmax]==-1)
					g1<<"Imposibil";
				else
					g1<<cmax[gmax]<<"\n";
					return 0;
}