#include <cstdio>
#include <algorithm>
using namespace std;
int v[805];
int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    int nrtri=0,i,n,aux,j;
    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){
        aux=j;
    while(aux<n&&v[i]+v[j]>=v[aux+1])
        aux++;
    nrtri=nrtri+aux-j;
        }
        printf("%d",nrtri);
}