#include <fstream>
#include <algorithm>
using namespace std;

int v[801];

ifstream fin("nrtri.in");
ofstream fout("nrtri.out");

int main(){
    int a,i,i2,i3,x,y,z,k=0;
    fin>>a;
    for(i=1;i<=a;i++){
        fin>>v[i];
    }
    sort(v+1,v+1+a);
    for(i=1;i<=a;i++){
        x=v[i];
        i2=i+1;
        while(i2<=a){
            y=v[i2];
            i3=i+2;
            i2++;
            if(y>2*x) i2=2000000000;
            else {
                while(i3<=a){
                z=v[i3];
                if(x+y>z) k++;
                else if(x+y<z) i3=2000000000;
                i3++;
                }
            }

        }
    }
    fout<<k;
    return 0;
}