#include<bits/stdc++.h>
using namespace std;
int n,m,ans,t,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;
}
/**************************************************************
	Problem: 1485
	User: yangjunwen
	Language: C++
	Result: Accepted
	Time:58 ms
	Memory:2152 kb
****************************************************************/