Please help me with the error.

[gamerrk1004]

The code prints the same output "NO" every time. Please someone help me with what the error can be.

#include<iostream>
using namespace std;

int main() 
{
	int n,q,i,j;
	int a,b,c,d;
	cin >> n >> q;
	int ar[n];
	for(j=0;j<n;j++)
	{
	     cin >> ar[j];
	}
	for(i=0;i<q;i++)
	{
	     int l,r;
	     cin >> l >> r;
	     ar[l-1]=a;
	     ar[l]=b;
	     ar[r-2]=c;
	     ar[r-1]=d;
	     
	     if(a<b)
	     {
	          if(c>d)
	          {
	               cout << "YES" << endl;
	          }
	          else 
	          {
	               cout << "NO" << endl;
	          }
	     }
	     else
	     {
	          if(c<d)
	          {
	               cout << "YES" << endl;
	          }
	          else 
	          {
	               cout << "NO" << endl;
	          }
	     }

	 } 
	 return 0;
}