#include<cstdio>
#define INF 2000000000
int G, W, e[10002], c[10002], i, j, a[15005], Max, Min=INF,sen;
int main()
{
	freopen("energii.in", "r", stdin);
	freopen("energii.out", "w", stdout);
	
	scanf("%d%d",&G, &W);
	for(i=1;i<=G;i++)
	{
		scanf("%d%d", &e[i], &c[i]);
        sen += e[i];
		if(Max < e[i])
		{
			Max = e[i];
		}
	}
	if(sen>=W)
    {
        for(i=1;i<=W+Max;i++)
        {
            a[i] = INF;
        }
	
        for(i=1;i<=G;i++)
        {
            for(j=W;j>=0;j--)
            {
                if(a[j] != INF)
                {
                    a[j+e[i]] = a[j] + c[i];
                }
            }
        }
	
        for(i=W;i<=W+Max;i++)
        {
            if(Min>a[i])
            {
                Min = a[i];
            }
        }
        printf("%d", Min);
    }
    else printf("-1");
	return 0;
}