#include <bits/stdc++.h>
#include <variant>

#define rep2(i,k,n) for(i64 i=(i64)(k);i<(i64)(n);i++)
#define rep(i,n) rep2(i,0,n)
#define all(x) begin(x),end(x)
#ifdef ENV_LOCAL
#define dump if (1) cerr
#else
#define dump if (0) cerr
#endif

using namespace std;
using namespace std::string_literals;

using i32 = int32_t;
using i64 = int64_t;
using f64 = double;
using f80 = long double;
using vi32 = vector<i32>;
using vi64 = vector<i64>;

//using namespace harudake;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  i64 n;
  cin>>n;
  i64 last = -1;
  i64 ans = n * (n+1) / 2;
  rep(i,n) {
    i32 a;
    cin>>a;
    if (a) {
      ans -= i - last;
    } else {
      last = i;
    }
  }
  cout<<ans<<endl;
  return 0;
}