#include<stdio.h>

#define MaxN 11000
#define INF 1012100
#define ll long long

ll W[MaxN];
int G;
int Wacc;
int a;
int b;
ll MIN = INF;

int main()
{
	FILE *f = fopen("energii.in","r");
	FILE *g = fopen("energii.out","w");
	
	fscanf(f,"%d %d",&G,&Wacc);
	for(int i=1;i<=Wacc;i++)
		W[i] = INF;
	for(int j=1;j<=G;j++)
	{
		fscanf(f,"%d %d",&a,&b);
		for(int i=Wacc-1;i;i--)
		{
			if(a + i < Wacc && W[i + a] > W[i] + b)
				W[i + a] = W[i] + b;
			if(i + a >= Wacc && W[i] + b < MIN)
				MIN = W[i] + b;
		}
		if(W[a]>b && a < Wacc)
			W[a] = b;	
		if(a >= Wacc && b < MIN)
			MIN = b;
	}
	if(MIN == INF)
		fprintf(g,"-1");
	else
		fprintf(g,"%llu",MIN);
	
	fclose(g);
	fclose(f);
	return 0;
}