#include <bits/stdc++.h>
#include <atcoder/modint>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
//using mint = modint1000000007;
using ll = long long;
using ld = long double;
using pll = pair<ll, ll>;
using tlll = tuple<ll, ll, ll>;
constexpr ll INF = 1LL << 60;
template<class T> bool chmin(T& a, T b) {if (a > b) {a = b; return true;} return false;}
template<class T> bool chmax(T& a, T b) {if (a < b) {a = b; return true;} return false;}
ll safemod(ll A, ll M) {return (A % M + M) % M;}
ll divfloor(ll A, ll B) {if (B < 0) {return divfloor(-A, -B);} return (A - safemod(A, B)) / B;}
ll divceil(ll A, ll B) {if (B < 0) {return divceil(-A, -B);} return divfloor(A + B - 1, B);}
#define FINALANS(A) do {cout << (A) << '\n'; exit(0);} while (false)

vector<ll> f(ll N, vector<ll> &A)
{
  vector<ll> ret(N);
  ret.at(N - 1) = (A.at(N - 1) == 0 ? N - 1 : N);
  for (ll i = N - 1; i > 0; i--)
  {
    ret.at(i - 1) = (A.at(i - 1) == 0 ? i - 1 : ret.at(i));
  }
  /*
  for (ll i = 0; i < N; i++)
  {
    cerr << ret.at(i) << " ";
  }
  cerr << endl;
  //*/
  return ret;
}

ll g(ll N, vector<ll> &A, ll k)
{
  auto B = f(N, A);
  ll ret = 0;
  for (ll i = k; i < N - 1; i += 2)
  {
    if (A.at(i) == 1)
    {
      ll tmp = B.at(i) - i;
      ret += tmp;
    }
  }
  //cerr << ret << endl;
  return ret;
}

int main()
{
  ll N;
  cin >> N;
  vector<ll> A(N);
  for (ll i = 0; i < N; i++)
  {
    cin >> A.at(i);
  }

  vector<ll> B(N);
  for (ll i = 0; i < N; i++)
  {
    B.at(i) = (i % 2 == 0 ? A.at(i) : 1 - A.at(i));
    //cerr << B.at(i) << " ";
  }
  //cerr << endl;
  vector<ll> C(N);
  for (ll i = 0; i < N; i++)
  {
    C.at(i) = (i % 2 == 1 ? A.at(i) : 1 - A.at(i));
    //cerr << C.at(i) << " ";
  }
  //cerr << endl;
  B.back() = 0, C.back() = 0;

  ll ans = g(N, B, 0) + g(N, C, 1);
  cout << ans << endl;
}