#include<cstdio>

#include<algorithm>

#include<cstring>

using namespace std;

int cnt,n,lim,s,root,sz[10000005],a[1000005],ls[10000005],rs[10000005];

long long ans,tr[10000005];

void update(int x){

	sz[x]=sz[ls[x]]+sz[rs[x]];

	tr[x]=tr[ls[x]]+tr[rs[x]];

}

void insert(int &t,int l,int r,int x){

	if (!t) t=++cnt;

	if (l==r){

		sz[t]++;

		tr[t]+=x;

		return;

	}

	int mid=(l+r)>>1;

	if (x<=mid) insert(ls[t],l,mid,x);

	else insert(rs[t],mid+1,r,x);

	update(t);

}

long long query(int t,int l,int r,int x){

	if (!x) return 0;

	if (!t) return 0;

	if (l==r) return 1ll*l*x;

	int mid=(l+r)>>1;

	if (sz[ls[t]]<=x) return query(rs[t],mid+1,r,x-sz[ls[t]])+tr[ls[t]];

	else return query(ls[t],l,mid,x);

}

void solve(){

	int Lim=lim;

	if (Lim>n-2) return;

	cnt=0;

	root=0;

	memset(ls,0,sizeof(ls));

	memset(rs,0,sizeof(rs));

	memset(tr,0,sizeof(tr));

	memset(sz,0,sizeof(sz));

	long long ANS=a[n]+a[s];

	Lim-=s-1;

	if (Lim<=0) ans=min(ans,ANS);

	for (int i=s+1; i<n; i++){

		insert(root,0,1e9,a[i+1]-a[i]);

		long long ANS1=ANS+a[n]-a[i+1];

		int l=Lim-(n-(i+1));

		if (l>0) ANS1+=query(root,0,1e9,l)*2;

		if (l>=0) ans=min(ans,ANS1);

	}

}

int main(){

	scanf("%d%d%d",&n,&lim,&s);

	for (int i=1; i<=n; i++) scanf("%d",&a[i]);

	ans=1ll<<60;

	if (s!=n && n-2<lim || !lim || s==n && n-1<lim){

		printf("-1\n");

		return 0;

	}

	solve();

	for (int i=1; i<=n/2; i++) swap(a[i],a[n-i+1]);

	for (int i=n; i>=1; i--) a[i]=a[1]-a[i];

	lim=n-lim-1;

	s=n-s+1;

	solve();

	if (ans!=1ll<<60) printf("%lld\n",ans);

	else printf("-1\n");

	return 0;

}

/*

8 4 1

0 99 142 209 398 493 571 652 685

992

8 0 2

0 3 30 124 153 160 199 216 270

*/