#include <bits/stdc++.h>

using namespace std;
const int N = 1e5+5;
typedef long long ll;
int n; ll d[N], ans, k;

int main () {
	freopen("kanmoo.in", "r", stdin);
	freopen("kanmoo.out", "w", stdout);
	scanf("%d%lld", &n, &k);
	for (int i = 1;i <= n;i++) scanf("%lld", &d[i]);
	ans = k+1;
	for (int i = 2;i <= n;i++) {
		if (d[i]-d[i-1] > k) ans += k+1;
		else ans += d[i]-d[i-1];
	}
	printf("%lld\n", ans);
	return 0;
}