#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

vector<int> v;
int n,s=0;

int bin_search_low(int x)
{
    int i = 0, pas = (1 << 16);
    while (pas != 0)
    {
        if (i + pas <= n && v[i + pas] <= x)
            i += pas;
        pas /= 2;
    }
    if (v[i]!=x) --i;
    if (i-1<=0) return 0;
    else
    return i-1;
}

void read()
{
    ifstream f ("nrtri.in");
    f>>n;
    v.resize(n);
    for (int i=0; i<n; ++i)
        f>>v[i];
}

int partition(int low,int high)
{
    int mid=(low+high)/2,pivot=v[mid],i=low-1,j=high+1;
LOOP:
    do ++i;
    while (v[i]<pivot);
    do --j;
    while (v[j]>pivot);
    if (i>=j)
        return j;
    swap(v[i],v[j]);
    goto LOOP;
}

void quicksort(int low,int high)
{
    if (low<high)
    {
        int pivot=partition(low,high);
        quicksort(low,pivot);
        quicksort(pivot+1,high);
    }
}

void solve()
{
    quicksort(0,n-1);
    for (int i=0; i<n-2; ++i)
        for (int j=i+1; j<n-1; ++j)
            s+=bin_search_low(v[i]+v[j]);
}

int main()
{
    read();
    solve();
    ofstream t ("nrtri.out");
    t<<s;
    return 0;
}