#include <stdio.h>
#include <assert.h>
#include <string.h>

enum { max_cost = 10001, max_items = 1002, inf = 0x3F3F3F3F };

int items, wanted;
int item[max_items][2]; // [0] - energy; [1] - cost
int cost[max_items][max_cost]; //cost[i][j] = min cost of having j energy with items 0..i
int ans;

void go()
{
	int i, j;

	memset(cost, 0x3F, sizeof(cost));
	cost[0][0] = 0;

	for(i = 1; i <= items; i++) //1-based! subtract 1
	{
		for(j = 0; j < max_cost; j++)
		{
			cost[i][j] = cost[i - 1][j]; //don't use this item

			if(j - item[i - 1][0] >= 0) //May Be Optimized (tm)
			{
				int tmp = cost[i - 1][ j - item[i - 1][0] ] + item[i - 1][1];
				if(cost[i][j] > tmp)
					cost[i][j] = tmp;
			}

			//if(cost[i][j] != inf)
			//	printf("cost items %d energy %d: %d\n", i, j, cost[i][j]);

			assert(cost[i][j] >= 0 && cost[i][j] <= inf);
		}

		//printf("\n");
	}

	ans = inf;
	for(i = wanted; i < max_cost; i++)
		if(cost[items][i] < ans)
			ans = cost[items][i];

	if(ans == inf)
		ans = -1; //not enough energy

	printf("ans %d\n", ans);
}

int main()
{
	int i;
	FILE *f = fopen("energii.in", "r");
	if(!f) return 1;
	
	fscanf(f, "%d%d", &items, &wanted);
	for(i = 0; i < items; i++)
		fscanf(f, "%d%d", &item[i][0], &item[i][1]);

	fclose(f);
	f = fopen("energii.out", "w");
	if(!f) return 1;

	go();

	fprintf(f, "%d\n", ans);
	fclose(f);
	return 0;
}