#include<bits/stdc++.h>
using namespace std;

int main(){
    int pricesSize,fee;
    cin >> pricesSize >> fee;
    int prices[pricesSize];
    for(int i = 0;i < pricesSize;i ++)
        cin >> prices[i];

    int hode = INT_MIN + fee,cash = 0,i = 0,bh_hode = hode;

    for(i = 0;i < pricesSize;i++){
        hode = max(hode,cash - prices[i]);
        cash = max(bh_hode + prices[i] - fee,cash);
        bh_hode = hode;
    }
    cout << cash;
    return 0;
}