#include <bits/stdc++.h>
using namespace std;

int count(vector<int>&arr , int k){
    unordered_map<int,int>hmap;
    int cnt=0; 
    for(int i=0;i<arr.size();i++){
       
        
        if(hmap.find(k+arr[i])!=hmap.end() ){
            cnt+=hmap[k+arr[i]];
        }
        if(k!=0 && hmap.find(arr[i]-k)!=hmap.end()){
            cnt+=hmap[arr[i]-k];
        }
        hmap[arr[i]]++;

    }
return cnt;    
}
int main(){
    vector<int> arr={1, 5, 3, 4, 2};
    int k=2;

    cout<<count(arr,k);

}