#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define REP(i,m,n) for(int i=(int)(m); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define RREP(i,m,n) for(int i=(int)(m); i>=(int)(n); i--)
#define rrep(i,n) RREP(i,(n)-1,0)
#define all(v) v.begin(), v.end()
#define endk '\n'
const int inf = 1e9+7;
const ll longinf = 1LL<<60;
const ll mod = 1e9+7;
const ll mod2 = 998244353;
const ld eps = 1e-10;
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;}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int n; cin >> n;
  vector<int> A(n);
  rep(i, n) {
    cin >> A[i];
    if(i&1) A[i] = 1-A[i];
  }
  vector<int> P;
  rep(i, n) {
    if(i && A[i] != A[i-1]) P.push_back(i);
  }
  P.push_back(n-1);
  ll ans = 0;
  rep(i, n-1) {
    if(i&1) {
      if(A[i]) continue;
    } else {
      if(!A[i]) continue;
    }
    ans += *lower_bound(all(P), i+1) - i;
  }
  cout << ans << endk;
  return 0;
}