#include<bits/stdc++.h>
using namespace std;
int n,m,ans,t,a[10005];
int main(){
	cin>>n>>m;
	if(m>=n) m=n;
	for(int i=1;i<=n;i++){
		cin>>a[i];
	}
	t=m+1;
	while(t<=m+n){
		for(int i=1;i<=m;i++){
			a[i]--;
			if(a[i]==0){
				a[i]=a[t];
				t++;
			}
		}
		ans++;
	}
	cout<<ans;

	return 0;
}

/**************************************************************
	Problem: 1485
	User: laichenxu
	Language: C++
	Result: Wrong Answer
****************************************************************/