#include <fstream>
#include <cstdio>
#include <algorithm>
using namespace std;
int n,i,v[810],j,k,nr;
int main(){
    freopen("nrtri.in","r",stdin);
    ofstream g ("nrtri.out");
    scanf("%d",&n);
    for(i=1;i<=n;++i)
    scanf("%d",&v[i]);
    sort(v+1,v+n+1);
    for(i=1;i<=n;++i)
    for(j=i+1;j<=n;++j)
    for(k=j+1;k<=n;++k)
    if(v[i]+v[j]>=v[k])++nr;
    else break;
    g<<nr;
    return 0;}