#include<stdio.h>

const char in[]="energii.in";
const char out[]="energii.out";
const int N=1005;

int c[N], w[N], a[N], G, W, k=0;

inline int max(int x, int y)
	{
		return x>=y? x :y;
}

int main()
	{
	freopen(in,"r",stdin);
	freopen(out,"w",stdout);
		int i, j;
		scanf("%d%d", &G, &W);
		for(i=1;i<=G && !k;++i)
		{scanf("%d%d", &c[i], &w[i]); 
			for(j=1;j<=i;++j)
			{
				a[i]=max(c[j] + a[i - j] ,  w[j]);
			if(a[i]>=W){k=a[i];break;}
			}
		}
		if(!k)printf("-1\n");
		else printf("%d\n", k);
	return 0;
}