#include<iostream>

using namespace std;
const int N = 1e5 + 10, INF = 0x3f3f3f3f;
int f[N][3], w[N];

int main() {
    int n, m;
    cin >> n;
    for (int i = 1; i <= n; i++) cin >> w[i];

    f[0][0] = f[0][1] = -INF, f[0][2] = 0;
    for (int i = 1; i <= n; i++) {
        f[i][0] = max(f[i - 1][0], f[i - 1][2] - w[i]);
        f[i][1] = f[i - 1][0] + w[i];
        f[i][2] = max(f[i - 1][2], f[i - 1][1]);

    }

    cout << max(f[n][1], f[n][2]);
}