#include <cstdio>

#include <iostream>

#include <algorithm>

#include <ios>

#include <vector>

using namespace std;

typedef long long ll;

const int N = (int)1e5;

int n, m, a[N + ];

vector<int> b[N + ];

int main(int argc, char *argv[]) {

//    freopen("note.in", "r", stdin);

//    freopen("note.out", "w", stdout);

    ios :: sync_with_stdio(false);//让cin跑快点。（别轻易用）

    cin >> n >> m;

    for (int i = ; i <= m; ++i) cin >> a[i];

    for (int i = ; i <= m; ++i) {

        if (i >  && a[i - ] != a[i]) b[a[i - ]].push_back(a[i]);

        if (i < m && a[i + ] != a[i]) b[a[i + ]].push_back(a[i]);

    }//找附近的元素。

    ll ans = 0LL, sum = 0LL;

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

        if (!b[i].size()) continue;

        sort(b[i].begin(), b[i].end());

        int y = b[i][b[i].size() >> ];

        ll before = 0LL, after = 0LL;

        for (int j = ; j < b[i].size(); ++j) {

            before += abs(i - b[i][j]);

            after += abs(y - b[i][j]);

        }

        ans = max(ans, before - after), sum += before;

    }

    cout << sum /  - ans << endl;//因为加了两边，所以/2。

    fclose(stdin);

    fclose(stdout);

    return ;

}