#include <bits/stdc++.h>
using namespace std;

ifstream in("energii.in");
ofstream out("energii.out");

int w,g,eg[1005],ec[1005];
void read(){
in>>g>>w;
for(int i=1;i<=g;i++)
in>>eg[i]>>ec[i];
}

void solve(){
int s=0,s1=0,mini=99999999,ok=0;
for(int i=1;i<=g;i++)
for(int j=i;j<=g;j++)
{
 s=0;
 s1=0;
 s=s+eg[j];
 s1=s1+ec[j];
 if(s>=w&&s1<mini){
  mini=s1;
  ok=1;
 }
}
if(ok==1)
out<<mini;
else out<<-1;
}


int main(){
read();
solve();

return 0;

}