#include <cstdio>
#include <algorithm>

using namespace std;

int v[810];

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