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#include <bits/stdc++.h>

using namespace std;
#define PB push_back
#define LL long long
#define int LL
#define FOR(i,a,b) for (int i = (a); i <= (b); i++)
#define FORD(i,a,b) for (int i = (a); i >= (b); i--)
#define REP(i,n) FOR(i,0,(int)(n)-1)
#define st first
#define nd second
#define ALL(x) (x).begin(), (x).end()
#define SZ(x) ((int)(x).size())
#define VI vector<int>
#define PII pair<int,int>
#define LD long double

template<class C> void mini(C& a4, C b4) { a4 = min(a4, b4); }
template<class C> void maxi(C& a4, C b4) { a4 = max(a4, b4); }

template<class TH> void _dbg(const char *sdbg, TH h){cerr<<sdbg<<"="<<h<<"\n";}
template<class TH, class... TA> void _dbg(const char *sdbg, TH h, TA... a) {
  while(*sdbg!=',')cerr<<*sdbg++;
  cerr<<"="<<h<<","; _dbg(sdbg+1, a...);
}

template<class T> ostream &operator<<(ostream &os, vector<T> V){
  os<<"[";for(auto vv:V)os<<vv<<",";return os<<"]";
} 

template<class L, class R> ostream &operator<<(ostream &os, pair<L,R> P) {
  return os << "(" << P.st << "," << P.nd << ")";
}


#ifdef LOCAL
#define debug(...) _dbg(#__VA_ARGS__, __VA_ARGS__)
#else
#define debug(...) (__VA_ARGS__)
#define cerr if(0)cout
#endif

int recursive_solve(VI a, int k){
    // find max idx
    int max_idx = max_element(ALL(a)) - a.begin();
    int res = 0;
    if(max_idx != 0){
        int desired = max(a[max_idx - 1], a[max_idx] - k);
        res += desired - a[max_idx - 1];
        a[max_idx - 1] = desired;
        res += recursive_solve(VI(a.begin(), a.begin() + max_idx), k);
    }
    if(max_idx != SZ(a) - 1){
        int desired = max(a[max_idx + 1], a[max_idx] - k);
        res += desired - a[max_idx + 1];
        a[max_idx + 1] = desired;
        res += recursive_solve(VI(a.begin() + max_idx + 1, a.end()), k);
    }
    return res;
}

int32_t main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout << fixed << setprecision(11);
  cerr << fixed << setprecision(6);
  int n, k;
  cin >> n >> k;
  vector<int> a(n);
  REP(i, n) cin >> a[i];
  cout << recursive_solve(a, k) << "\n";
}