#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 1000000007;
// constexpr int MOD = 998244353;
constexpr int DY[]{1, 0, -1, 0}, DX[]{0, -1, 0, 1};
constexpr int DY8[]{1, 1, 0, -1, -1, -1, 0, 1}, DX8[]{0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U> inline bool chmax(T &a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U> inline bool chmin(T &a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << fixed << setprecision(20);
  }
} iosetup;

int main() {
  int n; cin >> n;
  vector<int> a(n); REP(i, n) cin >> a[i];
  ll ans = 0;
  for (int i = 1; i < n; i += 2) a[i] ^= 1;
  for (int i = 0; i < n;) {
    if (a[i] == 0) {
      ++i;
      continue;
    }
    int j = i + 1;
    while (j < n && a[j] == 1) ++j;
    for (int k = i + (i & 1); k < j; k += 2) ans += min(j, n - 1) - k;
    i = j;
  }
  REP(i, n) a[i] ^= 1;
  for (int i = 0; i < n;) {
    if (a[i] == 0) {
      ++i;
      continue;
    }
    int j = i + 1;
    while (j < n && a[j] == 1) ++j;
    for (int k = i + (i % 2 == 0); k < j; k += 2) ans += min(j, n - 1) - k;
    i = j;
  }
  cout << ans << '\n';
  return 0;
}