P1102

#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
map<LL, LL> mp;
long long n, m, ans, a[20001];
int main()
{
	cin >> n >> m;
	for(int i = 1; i <= n; ++i)
	{
		cin >> a[i];
		mp[a[i]]++;
		a[i] -= m;
	}
	for(int i = 1; i <= n; ++i)
	{
		ans += mp[a[i]];
	}
	cout << ans;
	return 0;
}

求助大佬