#include<bits/stdc++.h>
using namespace std;
int n,m,t,ans,a[20000];
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: wangsenlin
	Language: C++
	Result: Accepted
	Time:92 ms
	Memory:2152 kb
****************************************************************/