结果

#include<bits/stdc++.h>
#define N 14125000
using namespace std;
unsigned long long n,c,a[N],b[N],sum;
int main(){
    cin>>n>>c; 
    for (int i=1;i<=n;i++){
        cin>>a[i];
        b[a[i]]++; 
    }
    for (int i=1;i<=n;i++){
        if (a[i]<c) continue;
        sum+=b[a[i]-c];
    }
    cout<<sum; 
    return 0;
}