#include<bits/stdc++.h>
#define D(...) fprintf(stderr,__VA_ARGS__)
#define rep(i,a,b) for(int i=(a);i<=(b);++i)
#define per(i,a,b) for(int i=(a);i>=(b);--i)
#define pb push_back
#define eb emplace_back
#define SZ(x) ((int)(x).size())
using namespace std;
using LL=long long;
const int N=100005;
int n,w,t,id[N],_id[N];
LL x[N],ans[N];
struct DS{
	priority_queue<LL>q1;
	priority_queue<LL,vector<LL>,greater<LL> >q2;
	LL s;
	void clear(){
		D("clear\n");
		s=0;
		while(!q1.empty())q1.pop();
		while(!q2.empty())q2.pop();
	}
	int size()const{return SZ(q1)+SZ(q2);}
	void push(int x){
		D("push %d\n",x);
		q2.push(x);
	}
	LL query(int k){
		while(SZ(q1)<k){
			s+=q2.top();
			q1.push(q2.top());
			q2.pop();
		}
		while(SZ(q1)>k){
			s-=q1.top();
			q2.push(q1.top());
			q1.pop();
		}
		if(SZ(q1)&&SZ(q2)){
			while(q1.top()>q2.top()){
				LL x=q1.top();
				LL y=q2.top();
				s=s-x+y;
				q1.pop();
				q2.pop();
				q1.push(y),q2.push(x);
			}
		}
		assert(SZ(q1)==k);
		D("query %d = %lld\n",k,s);
		return s;
	}
}ds;
void solve(int w,int e){
	ds.clear();
	rep(i,0,n)id[i]=i;
	sort(id,id+n+1,[&](int lhs,int rhs){return x[lhs]<x[rhs];});
	rep(i,0,n)_id[id[i]]=i;
	int bg=_id[0];
	rep(ed,0,n)if(ed!=bg){ // id[ed] at x[id[ed]]
		if(ed<bg){
			int least_w=(bg!=0)+(ed!=n);
			int least_e=1;
			if(w>=least_w&&e>=least_e){
				ans[id[ed]]=min(ans[id[ed]],x[id[bg]]-x[id[0]]+x[id[n]]-x[id[0]]+x[id[n]]-x[id[ed]]);
			}
		}else{
			int least_w=(bg!=0)+(ed!=n);
			int most_w=bg+n-ed;
			if(w>=least_w&&w<=most_w){
				ans[id[ed]]=min(ans[id[ed]],x[id[bg]]-x[id[0]]+x[id[n]]-x[id[0]]+x[id[n]]-x[id[ed]]);
			}
			if(w>most_w){
				if(w<=most_w+ds.size()){
					ans[id[ed]]=min(ans[id[ed]],x[id[bg]]-x[id[0]]+x[id[n]]-x[id[0]]+x[id[n]]-x[id[ed]]+ds.query(w-most_w));
				}
			}
		}
		if(ed-1>bg){
			ds.push(x[id[ed]]-x[id[ed-1]]);
		}
	}
}
int main(){
#ifdef xay5421
	freopen("a.in","r",stdin);
#endif
	ios::sync_with_stdio(0),cin.tie(0);
	cin>>n>>w>>t;
	x[0]=0;
	rep(i,1,n)cin>>x[i];
	memset(ans,63,sizeof(ans));
	solve(w,n-w);
	rep(i,0,n)x[i]*=-1;
	solve(n-w,w);
	LL res;
	if(t==2){
		res=ans[n];
	}else{
		res=*min_element(ans+1,ans+n+1);
	}
	if(res>=1e18){
		puts("-1");
	}else{
		printf("%lld\n",res);
	}
	return 0;
}