#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i,n) for(int i=0;i<n;++i)
int main() {
    int n; cin >> n;
    vector<int> a(n);
    rep(i,n)cin >> a[i];
    auto b = a;
    for (int i = 1; i < n; i += 2)b[i] ^= 1;
    b.push_back(-1);
    int pre = n;
    vector<int> c(n);
    for(int i = n - 1; 0 <= i; --i) {
        if (b[i] != b[pre])pre = i;
        c[i] = pre + 1;
    }

    ll ans = 0;
    rep(i,n)if (a[i])ans += min(c[i], n - 1) - i;
    cout << ans << "\n";
    return 0;
}