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#include<bits/stdc++.h> using namespace std; long long a[82000000]; int main() { long long i ,m, k = 0, j,b; long long s=0; long long n; long long t=0; cin >> m>>b; for (k = 1; k <= m; k++) { cin>>n; a[n]++; if(n>s)s=n; } for (k = 1; k <= s-b+1; k++) { t+=a[k]*a[k+b]; } cout<<t; return 0; }