#include <iostream>
using namespace std;
const int N(10009),N2(109);
int w[N],hyd[N2];
int main()
{
    int n,m,ans(0);
    cin>>n>>m;
    for(int i=1;i<=n;i++)
        scanf("%d",&w[i]);
    for(int i=1;i<=m;i++)
        hyd[i]=w[i];
    for(int i=m+1;i<=n;)
    {
        for(int j=1;j<=m;j++)
        {
            hyd[j]--;
            if(hyd[j]==0)
            {
                hyd[j]=w[i];
                i++;
            }
        }
        ans++;
    }
    int t(0);
    for(int i=1;i<=m;i++)
        t=max(t,hyd[i]);
    ans+=t;
    cout<<ans<<endl;
    return 0;
}

/**************************************************************
	Problem: 2293
	User: admin
	Language: C++
	Result: Accepted
	Time:67 ms
	Memory:2112 kb
****************************************************************/