```C++
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll INF = (ll)4e18;

ll calculate(const vector<int>& slices) {
    int N = slices.size();
    int need = (N + 1) / 3;
    if (need == 0) return 0;
    vector<vector<ll>> dp(N, vector<ll>(need + 1, INF));
    for (int i = 0; i < N; ++i) dp[i][0] = 0;

    dp[0][1] = slices[0];
    if (N > 1) dp[1][1] = min<ll>(slices[0], slices[1]);

    for (int i = 2; i < N; ++i) {
        for (int j = 1; j <= need; ++j) {
            ll not_take = dp[i - 1][j];
            ll take = (dp[i - 2][j - 1] == INF) ? INF : dp[i - 2][j - 1] + slices[i];
            dp[i][j] = min(not_take, take);
        }
    }
    return dp[N - 1][need];
}

ll minSizeSlices(vector<int>& slices) {
    int N = slices.size();
    if (N == 0) return 0;
    if (N == 1) return slices[0];

    vector<int> v1(slices.begin() + 1, slices.end());
    vector<int> v2(slices.begin(), slices.end() - 1);
    ll a = calculate(v1);
    ll b = calculate(v2);
    return min(a, b);
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n;
    if (!(cin >> n)) return 0;
    vector<int> slices(n);
    for (int i = 0; i < n; ++i) cin >> slices[i];

    cout << minSizeSlices(slices) << "\n";
    return 0;
}