#include <bits/stdc++.h>
template<class T> inline bool chmin(T&a, T b){if(a > b){a = b; return true;}else{return false;}}
template<class T> inline bool chmax(T&a, T b){if(a < b){a = b; return true;}else{return false;}}
#define ll long long
#define double long double
#define rep(i,n) for(int i=0;i<(n);i++)
#define REP(i,n) for(int i=1;i<=(n);i++)
#define mod (ll)(1e9+7)
#define inf (ll)(3e18+7)
#define eps (double)(1e-9)
#define pi (double) acos(-1)
#define P pair<int,int>
#define PiP pair<int,pair<int,int>>
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
using namespace std;

int main() {
    int n;
    cin >> n;
    vector<ll> a(n);
    rep(i, n)cin >> a[i];
    ll one = 0, two = 0;
    ll cnt = 0, ans = 0;
    rep(i, n)one += (a[i] == 1);
    rep(i, n)two += (a[i] == 2);
    cnt += one*(one-1)/2;
    ans += one*(one-1);
    cnt += one*two;
    ans += one*two*3;
    cout << ans - cnt + n*(n-1)/2 << endl;
}