#include <cstdio>
        #include <algorithm>
        #include <vector>
        using namespace std;
        vector <int> v;
        int main()
        {
            int n, x, 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",&x);
                v.push_back(x);
            }
            sort(v.begin(),v.end());
            for (i=0; i<n-2; i++)
            {
                for (j=i+1; j<n-1; j++)
                {
                    for (k=j+1; k<n; k++)
                    {
                        if (v[i]+v[j]>v[k]) nr++;
                        else break;
                    }
                }
            }
            printf("%d",nr);
            fclose(stdin);
            fclose(stdout);
            return 0;
        }