#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;
int v[805];
int main()
{
    FILE *in,*out;
    in=fopen("nrtri.in","r");
    out=fopen("nrtri.out","w");
    int n,i,j,c=0;
    long long nr=0;
    long long x;
    fscanf(in,"%d",&n);
    for(i=1;i<=n;i++)
        fscanf(in,"%d",&v[i]);
    sort(v+1,v+n+1);
    for(i=1;i<=n-2;i++)
        for(j=i+1;j<=n-1;j++)
        {
            x=j+1;
            c=0;
            while(v[x]<v[i]+v[j])
            {
                c++;
                x++;
            }
            nr=nr+c;
        }
        fprintf(out,"%lld",nr);
    return 0;
}