#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
const int64_t INF = (1LL << 60);
const long double pi = acosl(1);
const int64_t mod = 998244353;
const int dx[4] = {0, 1, 0, -1};
const int dy[4] = {1, 0, -1, 0};
const int ddx[8] = {1, 0, -1, -1, -1, 0, 1, 1};
const int ddy[8] = {1, 1, 1, 0, -1, -1, -1, 0};
int64_t mid;
template <typename Monoid>
struct SegmentTree {
  using F = function<Monoid(Monoid, Monoid)>;
  int sz;
  vector<Monoid> seg;
  const F f;
  const Monoid M1;
  int _n;
  SegmentTree(int n, const F f, const Monoid &M1) : f(f), M1(M1) {
    _n = n;
    sz = 1;
    while (sz < n) sz <<= 1;
    seg.assign(2 * sz, M1);
  }
  void set(int k, const Monoid &x) { seg[k + sz] = x; }
  void build() {
    for (int k = sz - 1; k > 0; k--) {
      seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
    }
  }
  void update(int k, const Monoid &x) {
    k += sz;
    seg[k] = x;
    while (k >>= 1) {
      seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
    }
  }
  Monoid query(int a, int b) {
    Monoid L = M1, R = M1;
    for (a += sz, b += sz; a < b; a >>= 1, b >>= 1) {
      if (a & 1) L = f(L, seg[a++]);
      if (b & 1) R = f(seg[--b], R);
    }
    return f(L, R);
  }
  Monoid operator[](const int &k) const { return seg[k + sz]; }
  template <typename C>
  int find_subtree(int a, const C &check, Monoid &M, bool type) {
    while (a < sz) {
      Monoid nxt = type ? f(seg[2 * a + type], M) : f(M, seg[2 * a + type]);
      if (check(nxt))
        a = 2 * a + type;
      else
        M = nxt, a = 2 * a + 1 - type;
    }
    return a - sz;
  }
  template <typename C>
  int find_first(int a, const C &check) {
    Monoid L = M1;
    if (a <= 0) {
      if (check(f(L, seg[1]))) return find_subtree(1, check, L, false);
      return -1;
    }
    int b = sz;
    for (a += sz, b += sz; a < b; a >>= 1, b >>= 1) {
      if (a & 1) {
        Monoid nxt = f(L, seg[a]);
        if (check(nxt)) return find_subtree(a, check, L, false);
        L = nxt;
        ++a;
      }
    }
    return -1;
  }
  template <typename C>
  int find_last(int b, const C &check) {
    Monoid R = M1;
    if (b >= sz) {
      if (check(f(seg[1], R))) return find_subtree(1, check, R, true);
      return -1;
    }
    int a = sz;
    for (b += sz; a < b; a >>= 1, b >>= 1) {
      if (b & 1) {
        Monoid nxt = f(seg[--b], R);
        if (check(nxt)) return find_subtree(b, check, R, true);
        R = nxt;
      }
    }
    return -1;
  }
};
void solve() {
  int64_t n;
  cin >> n;
  vector<int64_t> p(n);
  for (int64_t i = 0; i < (int64_t)(n); i++) cin >> p[i];
  vector<int64_t> v;
  for (int64_t i = 0; i < (int64_t)(n); i++)
    if (p[i] == i + 1) v.push_back(i);
  int64_t N = v.size();
  v.push_back(-INF);
  v.push_back(INF);
  sort((v).begin(), (v).end());
  int64_t ans = 0;
  for (int64_t i = 1; i < N + 1; i++) {
    if (abs(v[i] - v[i - 1]) >= abs(v[i] - v[i + 1])) {
      ans += abs(v[i] - v[i + 1]);
      i++;
    } else
      ans += min(abs(v[i] - v[i - 1]), abs(v[i] - v[i + 1]));
  }
  cout << ans << endl;
}
signed main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout << fixed;
  cout << setprecision(30);
  solve();
}
