#include<stdio.h>

#define MaxN 5100
#define INF 1012100

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

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