#include <fstream>
        #include <cstdio>
        #include <algorithm>
        using namespace std;
        int a[2001];
        int main()
        {
            int n, i, j, k, nr=0;
            freopen("nrtri.in", "r", stdin);
            freopen("nrtri.out", "w", stdout);
            scanf("%d",&n);
            for (i=1; i<=n; i++) scanf("%d",&a[i]);
            sort(a+1,a+n+1);
            for (i=1; i<=n-2; i++)
            {
                for (j=i+1; j<=n-1; j++)
                {
                    for (k=j+1; k<=n; k++)
                    {
                        if (a[i]+a[j]>a[k]) nr++;
                        else break;
                    }
                }
            }
            printf("%d",nr);
            return 0;
        }