#include <stdio.h>
#include <algorithm>
using namespace std;
int v[801], cnt, j, ok, k;
int main(){
    freopen("nrtri.in", "r", stdin);
    freopen("nrtri.out", "w", stdout);
    int n;
    scanf("%d", &n);
    for(int i=1;i<=n;i++)
         scanf("%d", &v[i]);
    sort(v+1,v+n+1);
    for(int i=1; i<n-1; i++)
        for(j=i+1; j<n; j++){
            ok=1;
            k=j+1;
            while(ok==1 && k<=n){
            ok=0;
            if(v[i]+v[j]>=v[k]){
                cnt++;
                ok=1;
            }
            k++;
        }
    }
    printf("%d ", cnt);
    return 0;
}