#include <bits/stdc++.h>
#pragma GCC optimize("O3")
using namespace std;
typedef long long ll;
short v[806], n, s=0;
int cauta(int val){
    int index=0;
    for(int bit=16;bit>=0;bit--){
        index+=1<<bit;
        if(index>n) index -= 1<<bit;
        else if(v[index]>val) index -= 1<<bit;
    }
    return index;
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    freopen("nrtri.in", "r", stdin);
    freopen("nrtri.out", "w", stdout);
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>v[i];
    }
    sort(v+1,v+n+1);
    for(int i=1;i<n;i++){
        s+=cauta(v[i]+v[i+1])-i-1;
    }
    cout<<s;
    cout.flush();
}