#include <fstream>

using namespace std;
ifstream cin("nrtri.in");
ofstream cout("nrtri.out");
int v[800],f[3000];
int main() {
    int n,a,st,dr,i,j,s;
    cin>>n;
    for(i=0; i<n; i++) {
        cin>>a;
        f[a]++;
    }
   /* j=0;
    for(i=0; i<30001; i++) {
        while(f[i]>0) {
            v[j]=i;
            j++;
            f[i]--;
        }
    }*/

    s=st=dr=0;
    for(i=n-1; i>0; i--) {
        st=0;
        dr=i-1;
        while(st<dr) {
            if(v[st]+v[dr]>v[i]) {
                s+=dr-st;
                dr--;
            } else
                st++;
        }
    }
    cout<<s;
    return 0;
}