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

int main(){
    int n; ll K;
    scanf("%d %lld",&n,&K);
    vector<ll> a(n+2,0);
    for(int i=1;i<=n;i++) scanf("%lld",&a[i]);

    ll base = 0; // cost / 2
    for(int i=0;i<=n;i++) if(a[i+1]>a[i]) base += a[i+1]-a[i];

    vector<pair<ll,ll>> nodes; // (width, levels)
    vector<pair<ll,int>> st;   // (height, left)
    for(int i=1;i<=n+1;i++){
        ll x = a[i];
        int left = i;
        while(!st.empty() && st.back().first > x){
            auto [h,l] = st.back(); st.pop_back();
            ll below = x;
            if(!st.empty()) below = max(below, st.back().first);
            nodes.push_back({(ll)(i-l), h-below});
            left = l;
        }
        if(x>0 && (st.empty() || st.back().first < x)) st.push_back({x,left});
    }

    sort(nodes.begin(), nodes.end());
    ll gain = 0;
    for(auto &[w,h] : nodes){
        ll t = min(h, K / w);
        gain += t;
        K -= t * w;
        if(t < h) break;
    }
    printf("%lld\n", 2*(base-gain));
    return 0;
}