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#pragma GCC optimize ("Ofast")
#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
#define FOR(i, a, b) for (auto i=(a); i<(b); i++)
#define FORD(i, a,  b) for (auto i=(a); i>(b); i--)
#define SZ(x) ((int)(x).size())
#define ITH_BIT(m, i) ((m)>>(i) & 1)
#define PPC(x) __builtin_popcount(x)

using namespace std;

#ifdef DEBUG
#include "debug.h"
#else
#define dbg(...) 0
#endif
template <typename T1, typename T2> inline void remin(T1& a, T2 b) { a = std::min(a, (T1)b);	}
template <typename T1, typename T2> inline void remax(T1& a, T2 b) { a = std::max(a, (T1)b);	}

const int maxN = 1 << 10, maxTS = maxN * 2, mod = 1'000'000'007;

int T[maxN];
bool done[maxN];

int maxInd(int n)
{
	int ret = n;
	FOR(i, 0, n)
		if (not done[i] and T[ret] < T[i])
			ret = i;
	return ret;
}

void solve()
{
	int n, k, x, res = 0;
	scanf ("%d%d", &n, &k);
	T[n] = -1;

	FOR(i, 0, n)
		scanf ("%d", T+i);
	while (T[x = maxInd(n)] != -1)
	{
		for (int i : {x-1, x+1}) if (0 <= i and i < n)
		{
			int d = std::max(0, T[x] - k - T[i]);
			res += d;
			T[i] += d;
		}
		done[x] = true;
	}
	printf("%d\n", res);
}

int main()
{
	int tc = 1;
//	scanf ("%d", &tc);	

	FOR(cid, 1, tc+1)
	{
//		printf("Case #%d: ", cid);
		solve();
	}
	return 0;
}