#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
#define rep(i,n) for (int i = 0; i < (n); i++)
#define REP(i,a,b) for(int i=(a);i<(b);i++)
#define all(v) begin(v),end(v)
#define rall(v) rbegin(v),rend(v)
#define fi first
#define se second
#define re0 return 0
template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using tup = tuple<ll, ll, ll>;
using cp = complex<double>;
constexpr ll inf = 2e9;
constexpr ll llinf = 9e18;
//constexpr ll MOD = 998244353;
constexpr ll MOD = 1000000007;
const double pai = acos(-1);

int main() {
    //cout<<fixed<<setprecision(15);
    ll n;cin>>n;
    vector<int> a(n);
    queue<int> cnt0;
    rep(i,n){
        cin>>a[i];
        if(a[i]==0)cnt0.push(i);
    }
    ll ans=0;
    rep(i,n){
        if(a[i]==0){
            ans+=n-i;
            cnt0.pop();
        }
        else {
            if(!cnt0.empty())ans+=n-i-1-(cnt0.front()-i-1);
        }
    }
    cout<<ans<<endl;
}