Here's my code, it works for every test I make, but it still gives WA on test #14

#include <stdio.h>

long a[50000],b[50000],ok=0,i,j=0,n,m;

main () {
     scanf ("%ld",&n);
     for (i=0;i<n;i++)
         scanf ("%ld",&a[i]);
     scanf ("%ld",&m);
     for (i=0;i<m;i++)
         scanf ("%ld",&b[i]);
     for (i=0;i<n;i++) {
         while ((a[i]+b[j]>10000)&&(j<m)) j++;
         if (a[i]+b[j]==10000) ok=1;}
     if (ok) printf ("YES");
     else printf ("NO");
}

Binary Search and accepted!