#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int n,s,i,j,nr,x,a[10001];
int main()
{fin>>n;
for(i=1;i<=n;i++){
    fin>>a[i];
}
sort(a+1,a+n+1);
for(i=1;i<=n;i++){
    for(j=i+1;j<n;j++){
        nr=a[i]+a[j];
        x=upper_bound(a+1,a+n+1,nr)-a;
        s=x-j-1+s;
    }
}
fout<<s;

    return 0;
}