#include <vector>
#include <cstdio>
#include <algorithm>

#define pb push_back

using namespace std;

vector < int > v ;
int main()
{
    freopen ("nrtri.in" , "r" , stdin);
    freopen ("nrtri.out" , "w" , stdout);
    int n;
    scanf ("%d" , &n );
    for ( int i = 1 ; i <= n ; ++i ){
        int x ;
        scanf ("%d",&x);
        v.pb(x);
    }
    sort(v.begin(),v.end());
    long long nr=0;
    for ( int i =0 ; i < n-2 ; ++i )
        for( int j=i+1 ; j < n-1 ; ++j )
            for ( int k=j+1 ; k < n ; ++k )
                if(v[i]+v[j]>=v[k])nr++;
                    else
                          break;
    printf ("%lld" , nr);
    return 0;
}