#include <iostream>
#include <fstream>

using namespace std;

int main()
{
fstream f,g;
f.open("nrtri.in",ios::in);
g.open("nrtri.out",ios::out);
int n,a[801],i,nr=0,j,k,ok;

f>>n;
for(i=1;i<=n;i++)
    f>>a[i];

do{
        ok=0;
        for(i=1;i<n;i++)
        if(a[i]>a[i+1]){
                k=a[i];
                a[i]=a[i+1];
                a[i+1]=k;
                ok=1;
        }
}while(ok==1);

for(i=1;i<n;i++)
    for(j=i+1;j<=n;j++){
        k=j+1;
        while(k<=n && a[i]+a[j]>=a[k]){
                k++;
                nr++;
        }
    }
g<<nr;}