#include <cstdio>
#include <algorithm>
#define MAX 12000000
#define MOD 104659
#define INF 6000000005
using namespace std;
  
char f[MAX];
int pos=0,N,MIN,S[20005]={},SOL=10000005;
struct arr
{
	int val,w;
}v[1005];
void r(int &nr)
{
    nr=0;
    while(f[pos]<'0'||f[pos]>'9')
        pos++;
    while(f[pos]>='0'&&f[pos]<='9')
        nr=nr*10+f[pos++]-'0';
}
int main()
{
    freopen("energii.in","r",stdin);
	freopen("energii.out","w",stdout);
    fread(f,1,MAX,stdin);
	r(N);r(MIN);
	for(int i=1;i<=20005;i++)
		S[i]=10000005;
	for(int i=1;i<=N;i++)
		r(v[i].val),r(v[i].w);
	for(int i=1;i<=N;i++)
	{
		for(int j=MIN;j>0;j--)
		{
			if(S[j]!=10000005)
				S[j+v[i].val]=min(S[j+v[i].val],S[j]+v[i].w);
		}
		S[v[i].val]=min(S[v[i].val],v[i].w);
	}
	for(int i=MIN;i<=20000;i++)
		if(S[i]<SOL)
			SOL=S[i];
	if(SOL!=10000005)
		printf("%d",SOL);
	else
		printf("-1");
	return 0;
}