//GIVE ME AC!!!!!!!!!!!!!!!!!
#pragma GCC target("avx")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include<bits/stdc++.h>
#define ll long long
#define floatset() fixed<<setprecision(15)
#define all(n) n.begin(),n.end()
#define rall(n) n.rbegin(),n.rend()
#define rep(i, s, n) for (ll i = s; i < (ll)(n); i++)
using namespace std;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
const ll inf =1e18;
const ll MOD=1000000007;
const ll mod=998244353;
const double pi=acos(-1);
using P=pair<ll,ll>;
int main(){
    ll n;
    cin>>n;
    vector<ll>a;
    a.push_back(0);
    a.push_back(n+1);
    rep(i,0,n){
        ll v;
        cin>>v;
        if(v==0){
            a.push_back(i+1);
        }
    }
    sort(all(a));
    ll ans=n*(n+1)/2;
    rep(i,1,a.size()){
        ll m=a[i]-a[i-1];
        ans-=m*(m-1)/2;
    }
    cout<<ans<<endl;
    
}