#include <stdio.h>
#include <algorithm>

using namespace std;

int v[810],n;

int main()
{
    int i,j,k,nr;
    freopen("nrtri.in","r",stdin);
    scanf("%d", &n);
    for (i=0;i<n;++i)
         scanf("%d", &v[i]);
    sort(v,v+n);
    for (i=0;i<n-2;++i)
    for (j=i+1;j<n-1;++j)
    for (k=j+1;k<n;++k)
    if (v[k]<=v[i]+v[j] && v[j]<=v[k]+v[i] && v[i]<=v[k]+v[j]) nr++;
        else break;
    freopen("nrtri.out","w",stdout);
    printf("%d",nr);
return 0;
}