#include <bits/stdc++.h>

using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
short int ct[30002],n,a[802];
long long sum;
int main()
{  fin>>n;
    for(short int i=1;i<=n;++i)
     {fin>>a[i];  ct[a[i]]++; }
    sort(a+1,a+n+1);
    for(short int i=1;i<=30001;++i)
        ct[i]+=ct[i-1];

    for(short int i=1;i<=n-2;++i)
        for(short int j=i+1;j<=n-1;++j)
           sum=sum+ct[ min(a[j]+a[i],30000) ]-j;
    fout<<sum;

    return 0;
}