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

using namespace std;

int v[801];

int main(){

    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);

    int n,i,putere,s,sum,j;

    scanf("%d",&n);
    for(i=1;i<=n;i++)
        scanf("%d",&v[i]);
    sort(v+1,v+n+1);

    sum=0;
    for(i=1;i<=n;i++){
        for(j=i+1;j<=n;j++){
            putere=1<<9;
            s=j;
            while(putere>0){
                if(s+putere<=n&&s+putere>j&&v[s+putere]<=v[i]+v[j])
                    s+=putere;
                putere/=2;
            }
            sum=sum+s-j;
        }
    }

    printf("%d",sum);

    return 0;
}