include<iostream>

include<algorithm>

using namespace std;

int main () {
int n;
cin >> n;
int a[n];
for (int i=0;i<n;i++) { cin >> a[i];
}
int dem=0;
sort (a,a+n);
int i=0,j=1,k=n-1;
while (true) {
while ((a[i]+a[j])<=a[k]) {
if (j<k-1) j++; else i++; if (i==(j-1) && j == (k-1) ) break; } if ( (a[i]+a[j])>a[k] && i<j && j < k) {
dem=dem+(k-j)*(j-i);
}
i=0;j=1;k=k-1;
if (k==1)break;
}
cout << dem;
}