#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); i++)
#define all(x) (x).begin(), (x).end()
using ll = long long;
using namespace std;
template <typename T> using vec = std::vector<T>;

int main() {
    int N;
    cin >> N;

    vec<int> Y(N);
    rep(i, N) cin >> Y[i];

    int ans = 0;
    rep(i, N) {
        int b = Y[i] - Y[max(i - 1, 0)];
        int n = Y[i] - Y[min(N - 1, i + 1)];

        if (b < 0) {
            ans += abs(b);
            Y[i] = Y[max(i - 1, 0)];

        } else if (b >= 0 && n >= 0 && b <= n) {
            ans += abs(b);
            Y[i] = Y[max(i - 1, 0)];
        } else if (b >= 0 && n >= 0 && b >= n) {
            ans += abs(n);
            Y[i] = Y[min(N - 1, i + 1)];
        }
    }
    
    cout << ans << endl;
}