#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define mid ((l+r)/2)
const int N=1e6+5,M=2e7+5,INF=2e9;
const ll INF1=1e18;
int n,m,c,type,a[N],ds[N];ll ans=INF1;
int cnts,rt;struct Seg {int vl1,ch[2];ll vl;}sg[M];
int New() {sg[++cnts]=(Seg) {0,{0,0},0};return cnts;}
void pu(int p)
{
    sg[p].vl=sg[sg[p].ch[0]].vl+sg[sg[p].ch[1]].vl;
    sg[p].vl1=sg[sg[p].ch[0]].vl1+sg[sg[p].ch[1]].vl1;
}
void upd(int &p,int l,int r,int x)
{
    if(!p) p=New();
    if(l==r) {++sg[p].vl1;sg[p].vl+=x;return;}
    if(x<=mid) upd(sg[p].ch[0],l,mid,x);
    else upd(sg[p].ch[1],mid+1,r,x);
    pu(p);
}
ll qry(int p,int l,int r,int x)
{
    if(l==r) return 1ll*min(sg[p].vl1,x)*l;
    int t=sg[sg[p].ch[0]].vl1;
    if(x<=t) return qry(sg[p].ch[0],l,mid,x);
    return sg[sg[p].ch[0]].vl+qry(sg[p].ch[1],mid+1,r,x-t);
}
void slv()
{
    int t=lower_bound(a+1,a+n+1,0)-a;
    cnts=rt=0;
    if(type==2 && m==1 && a[1]<0 && c>0)
        ans=min(ans,0ll+max(a[n],0)+(c-a[1])+max(a[n],0)-a[1]);
    if(t>n) return;
    if(!m && a[1]<0) return;
    if(m==n && a[n]>0) return;
    for(int i=t;i<=n;++i)
    {
        if(i>t) upd(rt,0,INF,a[i]-a[i-1]);
        if((c==INF || a[i]==c) && m>=(a[1]<0)+(i<n) && n-m>=(a[n]>0)+(i>t))
            ans=min(ans,qry(rt,0,INF,m-(t-1)-(n-i))*2+max(-a[1],0)*2+(a[n]-a[i])*2+a[i]);
    }
}
int main()
{
    scanf("%d %d %d",&n,&m,&type);
    for(int i=1;i<=n;++i) scanf("%d",&a[i]);
    if(type==2) c=a[n];else c=INF;
    sort(a+1,a+n+1);
    slv();
    for(int i=1;i<=n;++i) a[i]=-a[i];
    if(c!=INF) c=-c;
    reverse(a+1,a+n+1);
    m=n-m;
    slv();
    printf("%lld\n",ans<INF1?ans:-1);
    return 0;
}