#include <cstdio>
#include <algorithm>
#define DIM 850
using namespace std;

int v[DIM];

int main()
{

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

    int n, i, j, s, t, d, k;
    s = 0;

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

    sort( v + 1, v + 1 + n );

    for( i = 1; i < n - 1; ++i ){
        for( j = i + 1; j < n; ++j ){
            for( t = j + 1; t <= n; ++t ){
                if( v[i] + v[j] >= v[t] ) s++;
                else t = n + 1;
            }
        }
    }

    printf("%d",s);


    return 0;
}