Error in POLYNOM.cpp

[orientor]

even though i am getting a correct output in the program http://www.spoj.com/problems/POLYNOM/ ,SPOJ is teliing me that its WA.So,whats's the error in my program?

#include<iostream>
#include<cstdlib>
using namespace std;


    int main()
  { int N;
   cin>>N;
      bool flg=false;
      int i,j,k;
int d3,d2,d1,d0,f;
    for(i=1;i<=N;i++)
    {int n;
	cin>>n;
	if(n<1||n>500)
       {exit(0);}
int arr[501];
	for(j=0;j<n;j++)
        cin>>arr[j];
        for(d3=-50;d3<=50;d3++)
        {for(d2=-50;d2<=50;d2++)
            {for(d1=-50;d1<=50;d1++)
                {for(d0=-100;d0<=100;d0++)
                    {for(k=1;k<=n;k++)
                        {f=(d3*k*k*k)+(d2*k*k)+(d1*k)+(d0);
                            if(f==arr[k-1])
                            flg=true;
                            else
                           { flg=false;
                            break;}}
                            if(flg==true)
                           {

                            break;}}if(flg==true)
                            {break;}}if(flg==true)
                            {break;}}if(flg==true)
                            {break;}}if(flg==true)
                            {cout<<"YES";}
                            else
                            {cout<<"NO";}
                            arr[501]=NULL;
                            n=NULL;
                        }return 0;}

[kiner_shah]

Your program seems inefficient in terms of complexity, even though I havn't read the problem yet. Try improving the efficiency of your program. Find a way to reduce number of loops!