#pragma GCC optimize("Ofast,unroll-loops,no-stack-protector,fast-math,inline")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,lzcnt,mmx,abm,avx,avx2,fma")
#include <bits/stdc++.h>
using namespace std;
const int N = 2e5+1, inf = INT_MAX;
int n, m, mx, a[N];
map<int, int> dp[2];
signed main() {
ios::sync_with_stdio(false); cin.tie(nullptr);
cin >> n >> m;
a[0] = 0;
for (int i = 1; i <= n; i++) {
cin >> a[i];
}
dp[0][0] = 0;
for (int i = 1; i <= n; i++) {
dp[i%2].clear();
for (auto& [x, y] : dp[(i-1)%2]) {
if (y+m >= a[i]) {
auto it = dp[i%2].find(x);
if (it == dp[i%2].end()) dp[i%2][x] = a[i];
it->second = max(it->second, a[i]);
}
auto it = dp[i%2].find(x+1);
if (it == dp[i%2].end()) dp[i%2][x+1] = y+m;
it->second = max(it->second, y+m);
}
}
cout << dp[n%2].begin()->first << "\n";
}
