#define NDEBUG

#pragma GCC optimize ("O3") // 最適化レベルの変更 O0〜O3 などを指定
#pragma GCC optimize("-O3,inline,omit-frame-pointer,unroll-loops")
#pragma warning(1:4456) // 多重forループ内での変数の２重定義を警告にする

#define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES

#define ALL(a) (a).begin(),(a).end()

#include <iostream>
#include <array>
#include <vector>
#include <list>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <algorithm>
#include <numeric>
#include <iomanip>
#include <string>
#include <sstream>
#include <fstream>
#include <cmath>
#include <bitset>

#include <memory>
#include <cassert>

#include <functional>
#include <chrono>

using namespace std;

namespace ValLib {

	typedef unsigned int uint;
	typedef long long ll;
	typedef unsigned long long ull;

	template<typename T>void fill(vector<T>&vec,const T&value){std::fill(vec.begin(),vec.end(),value);}
	template<typename T>void fill(vector<vector<T>>&vec,const T&value){for(vector<T>&t:vec)std::fill(t.begin(),t.end(),value);}
	template<typename T>void resize(vector<T>&vec,int size1){vec.resize(size1);}
	template<typename T>void resize(vector<T>&vec,int size1,const T& value){vec.resize(size1,value);}
	template<typename T>void resize(vector<vector<T>>&vec,int size1,int size2){vec.resize(size1);for(vector<T>&t:vec)t.resize(size2);}
	template<typename T>void resize(vector<vector<T>>&vec,int size1,int size2,const T& value){vec.resize(size1);for(vector<T>&t:vec)t.resize(size2,value);}
	template<typename T>void assign(vector<T>&vec,int size1,const T& value){vec.assign(size1,value);}
	template<typename T>void assign(vector<vector<T>>&vec,int size1,int size2,const T& value){vec.resize(size1);for(vector<T>&t:vec)t.assign(size2,value);}
	template<typename T>bool contains(const vector<T>&vec,const T& val){return std::find(vec.begin(),vec.end(),val) != vec.end();}
	template<typename T,typename _Pr>bool contains_if(const vector<T>&vec,_Pr pred){return std::find_if(vec.begin(),vec.end(),pred)!=vec.end();}
	template<typename T,typename _Pr>typename iterator_traits<const typename vector<T>::const_iterator>::difference_type count_if(const vector<T>&vec,_Pr pred){return std::count_if(vec.begin(),vec.end(),pred);}
	template<typename T>void sort(vector<T>&vec){std::sort(vec.begin(),vec.end());}
	template<typename T,typename _Pr>void sort(vector<T>&vec,_Pr pred){std::sort(vec.begin(),vec.end(),pred);}
	template<typename T>void stable_sort(vector<T>&vec){std::stable_sort(vec.begin(),vec.end());}
	template<typename T,typename _Pr>void stable_sort(vector<T>&vec,_Pr pred){std::stable_sort(vec.begin(),vec.end(),pred);}

	template<typename T,size_t N>void fill(array<T,N>&ary,const T& value){std::fill(ary.begin(),ary.end(),value);}
	template<typename T,size_t N,size_t M>void fill(array<array<T,M>,N>&ary,const T& value){ for(array<T,M>& t : ary) std::fill(t.begin(),t.end(),value);}
	template<typename T,size_t N>bool contains(const array<T,N>&ary,const T& val){return std::find(ary.begin(),ary.end(),val)!=ary.end();}
	template<typename T,size_t N,typename _Pr>bool contains_if(const array<T,N>&ary,_Pr pred){return std::find_if(ary.begin(),ary.end(),pred) != ary.end();}
	template<typename T,size_t N,typename _Pr>typename iterator_traits<const typename array<T,N>::const_iterator>::difference_type count_if(const array<T,N>&ary,_Pr pred){return std::count_if(ary.begin(),ary.end(),pred);}
	template<typename T,size_t N>void sort(array<T,N>&ary){std::sort(ary.begin(),ary.end());}
	template<typename T,size_t N,typename _Pr>void sort(array<T,N>&ary,_Pr pred){std::sort(ary.begin(),ary.end(),pred);}
	template<typename T,size_t N>void stable_sort(array<T,N>&ary){std::stable_sort(ary.begin(),ary.end());}
	template<typename T,size_t N,typename _Pr>void stable_sort(array<T,N>&ary,_Pr pred){std::stable_sort(ary.begin(),ary.end(),pred);}


	template<typename A>void in(A&a){cin>>a;cin.ignore();}
	template<typename A,typename B>void in(A&a,B&b){cin>>a>>b;cin.ignore();}
	template<typename A,typename B,typename C>void in(A&a,B&b,C&c){cin>>a>>b>>c;cin.ignore();}
	template<typename A,typename B,typename C,typename D>void in(A&a,B&b,C&c,D&d){cin>>a>>b>>c>>d;cin.ignore();}
	template<typename A,typename B,typename C,typename D,typename E>void in(A&a,B&b,C&c,D&d,E&e){cin>>a>>b>>c>>d>>e;cin.ignore();}
	template<typename A,typename B,typename C,typename D,typename E,typename F>void in(A&a,B&b,C&c,D&d,E&e,F&f){cin>>a>>b>>c>>d>>e>>f;cin.ignore();}
	template<typename A,typename B,typename C,typename D,typename E,typename F,typename G>void in(A&a,B&b,C&c,D&d,E&e,F&f,G&g){cin>>a>>b>>c>>d>>e>>f>>g;cin.ignore();}

	template<typename A>
	void inr(vector<A>& a, int size) {
		resize(a, size);
		for (int i = 0; i < size; ++i) {
			cin >> a[i]; cin.ignore();
		}
	}
	template<typename A, typename B>
	void inr(vector<A>& a, vector<B>& b, int size) {
		resize(a, size); resize(b, size);
		for (int i = 0; i < size; ++i) {
			cin >> a[i] >> b[i]; cin.ignore();
		}
	}
	template<typename A, typename B, typename C>
	void inr(vector<A>& a, vector<B>& b, vector<C>& c, int size) {
		resize(a, size); resize(b, size); resize(c, size);
		for (int i = 0; i < size; ++i) {
			cin >> a[i] >> b[i] >> c[i]; cin.ignore();
		}
	}
	template<typename A, typename B, typename C, typename D>
	void inr(vector<A>& a, vector<B>& b, vector<C>& c, vector<D>& d, int size) {
		resize(a, size); resize(b, size); resize(c, size); resize(d, size);
		for (int i = 0; i < size; ++i) {
			cin >> a[i] >> b[i] >> c[i] >> d[i]; cin.ignore();
		}
	}
	template<typename A, typename B, typename C, typename D, typename E>
	void inr(vector<A>& a, vector<B>& b, vector<C>& c, vector<D>& d, vector<E>& e, int size) {
		resize(a, size); resize(b, size); resize(c, size); resize(d, size); resize(e, size);
		for (int i = 0; i < size; ++i) {
			cin >> a[i] >> b[i] >> c[i] >> d[i] >> e[i]; cin.ignore();
		}
	}

	template<typename A>
	void inr(vector<vector<A>>& a, int h, int wa) {
		resize(a, h, wa);
		for (int i = 0; i < h; ++i) {
			for (int j = 0; j < wa; ++j) {
				cin >> a[i][j];
			}
			cin.ignore();
		}
	}
	template<typename A,typename B>
	void inr(vector<vector<A>>& a, vector<vector<B>>& b, int h, int wa, int wb) {
		resize(a, h, wa); resize(b, h, wb);
		for (int i = 0; i < h; ++i) {
			for (int j = 0; j < wa; ++j) {
				cin >> a[i][j];
			}
			for (int j = 0; j < wb; ++j) {
				cin >> b[i][j];
			}
			cin.ignore();
		}
	}
	template<typename A,typename B,typename C>
	void inr(vector<vector<A>>& a, vector<vector<B>>& b, vector<vector<C>>& c, int h, int wa, int wb, int wc) {
		resize(a, h, wa); resize(b, h, wb); resize(c, h, wc);
		for (int i = 0; i < h; ++i) {
			for (int j = 0; j < wa; ++j) {
				cin >> a[i][j];
			}
			for (int j = 0; j < wb; ++j) {
				cin >> b[i][j];
			}
			for (int j = 0; j < wc; ++j) {
				cin >> c[i][j];
			}
			cin.ignore();
		}
	}

	template<typename T>
	void out(const T& val) { cout << val << endl; }
}

using namespace ValLib;

int main() {
	std::ios::sync_with_stdio(false);

	int n;
	cin >> n;
	
	int L[2 * 1000];
	for (int i = 0; i < n; ++i) {
		cin >> L[i];
	}

	sort(&L[0], &L[n - 1] + 1, less<int>());

	ll ans = 0;
	for (int i = 0; i < n; ++i) {
		for (int j = i + 1; j < n; ++j) {
			int ab = L[i] + L[j];
			for (int k = j + 1; k < n; ++k) {
				if (L[k] >= ab) {
					break;
				}
				++ans;
			}
		}
	}


	cout << ans << endl;

	getchar();
}


Measured memory_bytes: 256