#include<bits/stdc++.h>
using namespace std;
int n,m,ans,t,a[10005];
int main(){
	cin>>n>>m;
	for(int i=1;i<=n;i++){
		cin>>a[i];
	}
	if(n<=m) m=n;
	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: hulaoshi
	Language: C++
	Result: Wrong Answer
****************************************************************/