#include "books.h"
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ii pair<int,int>
#define fi first
#define se second
#define rep(x,s,e) for (auto x=(s)-((s)>(e));x!=(e)-((s)>(e));((s)<(e)?x++:x--))
#define all(x) (x).begin(),(x).end()
#define sz(x) (int) (x).size()
int n,k;
vector<int> arr;
int fwd[1000005];
int bwd[1000005];
long long minimum_walk(std::vector<int> p, int s) {
n=sz(p),k=s;
arr=p;
rep(x,0,n){
if (x<arr[x]) fwd[x]++,fwd[arr[x]]--;
else bwd[arr[x]]++,bwd[x]--;
}
rep(x,0,n) fwd[x+1]+=fwd[x],bwd[x+1]+=bwd[x];
ll ans=0;
rep(x,n,0){
int val=max(fwd[x],bwd[x]);
if (val==0){
if (ans) ans++;
}
else{
ans+=val;
}
}
return ans*2;
}
