#include<stdio.h>

int a[25600];

int main()
{
	freopen("energii.in", "r", stdin);
	freopen("energii.out", "w", stdout);
	int n, e, putere, cost, i, j, sol=0x7fffffff, b=0x7fffffff;
	scanf("%d %d", &n, &e);
	for (i=1; i<25600; i++)
		a[i]=0x3fffffff;
	
	for (i=1; i<=n; i++)
	{
		scanf("%d %d", &putere, &cost);
		for (j=e; j>=0; j--)
		{
			if (a[j]+cost<a[j+putere])
				a[j+putere]=a[j]+cost;
			if ((j+putere>=e) && (a[j+putere]<sol))
				sol=a[j+putere];
		}
	}
	if (sol!=b)
		printf("%d", sol);
	else
		printf("-1");
	return 0;
}