#include<fstream>
#include<algorithm>
using namespace std;
main()
{
short int s1,i,n, a[802];
int s,sum=0;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
f>>n;
for(i=1; i<=n; i++)
f>>a[i];
if(n>=3){
sort(a+1,a+n+1);
for(int j=1; j<n-1; j++)
{
    s=a[j]+a[j+1];
    for(i=j+2; i<=n; i++ )
            if(s>=a[i]) sum++; else break;
}
}
g<<sum;
}