#include<cstdio>
#include<algorithm>
using namespace std;
int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    int n,i,j,k,x[1001],nr=0;
    scanf("%d",&n);
    for(i=1;i<=n;i++)
        scanf("%d",&x[i]);
    sort(x+1,x+n+1);
    for(i=1;i<=n-2;i++)
        for(j=i+1;j<n;j++)
            for(k=j+1;k<=n && x[i]+x[j]>=x[k];k++)
                nr++;
    printf("%d\n",nr);
    return 0;
}