#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10;

int n;
int w[N];
int f[N][3];

int main() {
    scanf("%d", &n);
    for (int i = 1; i <= n; i++) scanf("%d", &w[i]);
    //无法判定或肯定不合理的
    memset(f, -0x3f, sizeof f);
    //这些状态是合理的
    for (int i = 0; i <= n; i++) f[i][0] = 0;
    //开始进行状态转移
    for (int i = 1; i <= n; ++i) {
        f[i][0] = max(f[i - 1][0], f[i - 1][2]);
        f[i][1] = max(f[i - 1][1], f[i - 1][0] - w[i]);
        f[i][2] = f[i - 1][1] + w[i];
    }
    printf("%d\n", max(f[n][0], f[n][2]));
    return 0;
}