//stringray

#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>

/*#ifndef __LOCAL__ 
#pragma comment(linker,"/stack:200000000")
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#endif*/ 

using namespace std;
using namespace __gnu_pbds;
 
//#define int int64_t

typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> ost;

typedef pair<int,int> pii;
typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<pii> vpii;
typedef vector<vi> vvi;
typedef vector<set<int>> vsi;

#define endl "\n"
#define all(x) x.begin(),x.end()
#define pb push_back
#define F first
#define S second
#define fore(i,a,b) for(int i=(a);i<=(b);++i)
#define rep(i,n) for(int i=0;i<n;++i)
#define sz(x) int(x.size())
#define debug(x) cout<<#x<<" "<<x<<endl
#define IOS  ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(0)


const int N1=100*1000;
const int N2=1000*1000;
const int mod=1e9+7;

int min3(int a,int b,int c){return min(a,min(b,c));}
int max3(int a,int b,int c){return max(a,max(b,c));}
int min4(int a,int b,int c,int d){return min(min(a,b),min(c,d));}
int max4(int a,int b,int c,int d){return max(max(a,b),max(c,d));}

template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}
template<typename T>
istream& operator >> (istream& is,vector<T>& vec){
  for(T &x:vec)is>>x;
  //for(int i=0;i<vec.size();++i)is>>x[i];
  return is;
}

template<typename T>
ostream& operator << (ostream& os,vector<T>& vec){
  for(int i=0;i<vec.size();++i){
    os<<vec[i]<<(i+1==vec.size()?"":" ");
  }
  return os;
}

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

const ll FIXED_RANDOM=chrono::steady_clock::now().time_since_epoch().count();

struct chash {
    static unsigned long long hash_f(unsigned long long x) {
        x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }
    static unsigned hash_combine(unsigned a, unsigned b) { return a * 31 + b; }
    int operator()(int x) const { return hash_f(x); }
};
//unordered_map <int, int, chash> m; way to use this 
//the way you're supposed to do is it by initializing FIXED_RANDOM with something like chrono::steady_clock::now().time_since_epoch().count()(current time in microseconds or something like that) and instead of hash_f(x) do hash_f(FIXED_RANDOM^x) 

int getRand(int l, int r)
{
	uniform_int_distribution<int> uid(l, r);
	return uid(rng);
}

ll mpow(ll a, ll b){
  ll ret=1;
  while(b>0){
    if(b&1LL)(ret*=a)%=mod;
    (a*=a)%=mod;
    b>>=1LL;
  }
  return ret;
}

void solve(){
  int n;cin>>n;
  vi v(n);
  rep(i,n)cin>>v[i];
  sort(all(v));
  int ans=0;
  for(int i=0;i<n;++i){
    for(int j=i+1;j<n;++j){
      if(j+1>=n)continue;
      auto it=lower_bound(v.begin()+j+1,v.end(),v[i]+v[j])-(v.begin());
      int diff=it-(j+1);
      ans+=diff;
      
    }
  }
  cout<<ans<<endl;
  
}
int32_t  main(){
  IOS;
  cout<<(fixed)<<setprecision(6);
  solve();
  return 0;
}



Measured memory_bytes: 256