#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef pair<ll,ll> P;
typedef vector<ll> VI;
typedef vector<VI> VVI;
#define REP(i,n) for(ll i=0;i<(n);i++)
#define ALL(v) v.begin(),v.end()
template<typename T> bool chmax(T &x, const T &y) {return (x<y)?(x=y,true):false;};
template<typename T> bool chmin(T &x, const T &y) {return (x>y)?(x=y,true):false;};
constexpr ll MOD=1000000007;
constexpr ll INF=2e18;

int main(){
    int n; cin >> n;
    VI a(n); REP(i,n) cin >> a[i];
    REP(i,n){
        if(i%2==1)
            a[i]=!a[i];
    }
    int x=0;
    ll ans=0;
    for(int i=n-1;i>=0;i--){
        if(i<n-1){
            if(a[i]==a[i+1])
                x++;
            else
                x=1;
        }
        if(i%2!=a[i])
            ans+=x;
    }
    cout << ans << endl;
    return 0;
}