#include<cstdio>
using namespace std;

int n,i,w,pw,cw,sum,ok;

int main () {
	freopen("energii.in","r",stdin);
	freopen("energii.out","w",stdout);
	scanf("%d",&n);
	scanf("%d",&w);
	for ( i = 1 ; i <= n ; i++ )
	{	scanf("%d%d",&pw,&cw);
		sum += pw;
		if( pw == w)
		{printf("%d",&cw);
		ok = 1;}
	}
	if(ok==0)
		if( sum < w ) 
			printf("-1\n");
	return 0;
}