#include<bits/stdc++.h>
using namespace std;
int main(){
    int n,m,w[20000],t,ans=0;
	cin>>n>>m;
	for(int i=1;i<=n;i++){
		cin>>w[i];
	}
	if(m>=n) m=n; 
	t=m+1;
	while(t<=m+n){
		for(int i=1;i<=m;i++){
			 w[i]--;
			 if(w[i]==0){
			 	w[i]=w[t];
			 	t++;
			 }
		}
		ans++;
	}
	cout<<ans;
	return 0;
}

/**************************************************************
	Problem: 1485
	User: duyahan
	Language: C++
	Result: Accepted
	Time:60 ms
	Memory:2072 kb
****************************************************************/