#include <bits/stdc++.h>
    using namespace std;
    #include <math.h>
    #include <iomanip>
    #include <cstdint>
    #include <string>
    #include <sstream>
    template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
    template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
    #define rep(i,n) for (int i = 0; i < (n); ++i)
    typedef long long ll;
    using P=pair<ll,ll>;
    const int INF=1001001001;
    const int mod=1e9+7;
    
    void solve(){
      int n;
      cin>>n;
      vector<int>a(n);
      rep(i,n){cin>>a[i];}
      ll ans=n*(n+1)/2;
      int i=0;
      while(i<n){
        while(i<n&&a[i]==0){i++;}
        ll cnt=0;
        while(i<n&&a[i]==1){i++;cnt++;}
        ans-=cnt*(cnt+1)/2;
      }
      cout<<ans<<endl;
    }
    int main(){
        solve();
        return 0;
    }