# include <bits/stdc++.h>
using namespace std;
ifstream fi("nrtri.in");
ofstream fo("nrtri.out");
int s[805];
int main(void)
{
    int n,ans=0;
    fi>>n;
    for (int i=1;i<=n;++i) fi>>s[i];
    sort(s+1,s+1+n);
    for (int i=1;i<=n;++i)
        for (int j=i+1;j<=n;++j)
           for (int x=j+1;x<=n && s[i]+s[j] >= s[x];++x) ++ans;
    return fo << ans << '\n',0;
}