#include<cstdio>
#include<algorithm>
using namespace std;

int N, i, S, sol, j, k;
int v[802];

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

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

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

        for (i = 1; i <= N - 2; i++)
            for (j = i + 1; j <= N - 1; j++)
            {
                S = v[i] + v[j];

                for (k = j + 1; k <= N; k++)
                    if (S >= v[k])
                        sol++;
                    else
                        break;
            }
        printf("%d\n", sol);
    }