#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main(){
  int N;
  cin>>N;
  vector<int> A={0};
  for(int i=1;i<=N;i++){
      int a;
      cin>>a;
      if(a == 0) A.push_back(i);
  }
  A.push_back(N+1);
  int ans = N*(N+1)/2;
  for(int i=0;i<A.size()-1;i++){
      int a = A[i+1]-A[i]-1;
      ans -= a*(a+1)/2;
  }
  cout<<ans<<endl;
}