#include "books.h"
#include <bits/stdc++.h>
#define forsn(i, s, n) for (int i = int(s); i < int(n); i++)
#define forn(i, n) forsn(i, 0, n)
#define dforsn(i, s, n) for (int i = int(n) - 1; i >= int(s); i--)
#define dforn(i, n) dforsn(i, 0, n)
#define sz(x) int(x.size())
#define all(x) begin(x), end(x)
#define pb push_back
#define eb emplace_back
#define fst first
#define snd second
using namespace std;
using vi = vector<int>;
using ii = pair<int, int>;
using ll = long long;
ll minimum_walk(vi p, int /*s*/) {
const int n = sz(p);
vi need(n + 1, 0);
forn(i, n) {
need[min(i, p[i])]++;
need[max(i, p[i])]--;
}
forn(i, n) need[i + 1] += need[i];
ll ret = 0;
dforn(i, n) {
ret += need[i];
if (!need[i] && ret > 0) ret += 2;
}
return ret;
}
