#include <iostream>
#include <fstream>

using namespace std;
int a[2100][2], m ,w;
void afisare(int k);
void testare ()
{
    int s =0 ;
    for ( int i = 0 ; i < m ; i++ )
       {

      s=s+a[i][1];
    }
    if(s<w)
    {
        afisare(0);
    }
}
void citire ()
{
    ifstream f ("energii.in");
    f>> w;
    for ( int i = 0 ; i < m ; i++ )
       {
    for ( int j = 0 ; i < 2 ; i++ )
      f>> a[i][j];
       }
       testare();
}

void afisare (int k=1)
{
    ofstream g ("energii.out");
    if (k==0)
    {
        g<<-1;
    }
}

int main()
{
    citire;
    return 0;
}