#define ll long long 
 // Yup it doesn't with LRU but OPT page replacement policy works. 
void solve()
{
  // A map to store all the occurences where a customer will arrive in near future.
  vector < set <ll> > v(405);
  
  cin >> n >> m;
  ll a[m];
  for(ll i=0;i<m;i++)
  {
    cin >> a[i];
    v[a[i]].insert(i);
  }
  
  ll ans=0;
  
  set <ll> table;
  ll i=0;
  // First fill all the empty tables.
  while(table.size()<n and i<m)
  {
    table.insert(a[i]);
    v[a[i]].erase(i);

Optimal page replacement policy can be used to solve this problem.