#include <iostream>
using namespace std;
const int N = 1e5 + 10, INF = 0x3f3f3f3f;
int n;
int w[N];
int f[N][2];
int x;
int main() {
    scanf("%d%d", &n, &x);
    for (int i = 1; i <= n; ++i) scanf("%d", &w[i]);

    f[0][1] = -INF;
    for (int i = 1; i <= n; ++i) {
        f[i][0] = max(f[i - 1][0], f[i - 1][1] + w[i] - x);
        f[i][1] = max(f[i - 1][1], f[i - 1][0] - w[i]);
    }
    printf("%d\n", f[n][0]);
    return 0;
}