#include <bits/stdc++.h>
using namespace std;
int count(int a[],int n,int k){
	int count=0;
	unordered_map<int,int>b;
	for(int i=0;i<n;i++){
		int x=k+a[i];
		int y=-k+a[i];
		if(b.find(x)!=b.end()){
			count+=b[x];
 
		}
		if(b.find(y)!=b.end()){
			count+=b[y];
 
		}
		b[a[i]]++;
	}
	return count;
 
}
 
int main() {
	// your code goes here
	int a[]={5,6,4,3,6};
	int n=sizeof(a)/sizeof(a[0]);
	int k=3;
	int ans=count(a,n,k);
	cout<<ans;
 
 
	return 0;
}

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