#include<stdio.h>
#include<algorithm>
using namespace std;
int s;
int main()
{
    int n,i,v[805],j,k;
    freopen("nrtri.in","r",stdin);
    scanf("%d",&n);for(i=1;i<=n;++i) scanf("%d",&v[i]);
    fclose(stdin);
    sort(v+1,v+1+n);
    for(i=n;i>1;--i)
        for(j=i-1;j;--j)
        {
            int a=v[i]-v[j];
            for(k=1;v[k]<a && k<j;++k);
            s+=j-k;
        }

    freopen("nrtri.out","w",stdout);printf("%d",s);
    fclose(stdout);
    return 0;
}