#include <cstdio>
#include <algorithm>

using namespace std;

int v[820];

int main() {
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    int n,sol=0,last;
    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 ; i++) {
        last=i+1;
        for (int j=i+1; j<=n; j++) {
            while(last<j)
                last++;
            while(last<n&&v[i]+v[j]>=v[last+1])
                last++;
            sol+=last-j;
        }
    }
    printf("%d\n",sol);
    return 0;
}