#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <cmath>
#include <vector>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <queue>
#include <ctime>
#include <cassert>
#include <complex>
#include <string>
#include <cstring>
#include <chrono>
#include <random>
#include <bitset>
#include <fstream>
#include <array>
#include <functional>
#include <stack>
#include <memory>
using namespace std;
#define int long long
#define ii pair <int, int>
#define app push_back
#define all(a) a.begin(), a.end()
#define bp __builtin_popcountll
#define ll long long
#define mp make_pair
#define x first
#define y second
#define Time (double)clock()/CLOCKS_PER_SEC
#define munq(a) sort(all(a)); a.resize(unique(all(a))-a.begin())
#define sz(a) ((int)a.size())

#ifdef LOCAL
#define debug(x) do { cout << #x << ": " << x << endl; } while(0)
#define debug2(x, y) do { std::cerr << #x << ", " << #y << ": " << x << ", " << y << endl; } while (0)
#define debug3(x, y, z) do {std::cerr << #x << ", " << #y << ", " << #z << ": " << x << ", " << y << ", " << z << endl; } while(0)
#else
#define debug(x)
#define debug2(x, y) 
#define debug3(x, y, z) 
#endif

#define FORI(i,a,b) for (int i = (a); i < (b); ++i)
#define FOR(i,a) FORI(i,0,a)
#define ROFI(i,a,b) for (int i = (b)-1; i >= (a); --i)
#define ROF(i,a) ROFI(i,0,a)
#define rep(a) FOR(_,a)
#define each(a,x) for (auto& a: x)
#define FORN(i, n) FORI(i, 1, n + 1)

using vi = vector<int>;
template <typename T>
std::istream& operator >>(std::istream& input, std::pair <T, T> & data)
{
    input >> data.x >> data.y;
    return input;
}
template <typename T>
std::istream& operator >>(std::istream& input, std::vector<T>& data)
{
    for (T& x : data)
        input >> x;
    return input;
}
template <typename T>
std::ostream& operator <<(std::ostream& output, const pair <T, T> & data)
{
    output << "(" << data.x << "," << data.y << ")";
    return output;
}
template <typename T>
std::ostream& operator <<(std::ostream& output, const std::vector<T>& data)
{
    for (const T& x : data)
        output << x << " ";
    return output;
}
ll div_up(ll a, ll b) { return a/b+((a^b)>0&&a%b); } // divide a by b rounded up
ll div_down(ll a, ll b) { return a/b-((a^b)<0&&a%b); } // divide a by b rounded down 
ll math_mod(ll a, ll b) { return a - b * div_down(a, b); }
#define tcT template<class T
#define tcTU tcT, class U
tcT> using V = vector<T>; 
tcT> bool ckmin(T& a, const T& b) {
    return b < a ? a = b, 1 : 0; 
} // set a = min(a,b)
tcT> bool ckmax(T& a, const T& b) {
    return a < b ? a = b, 1 : 0; 
}
tcT> vector <T> presum(vector <T> &a) {
    vector <T> p(a.size() + 1);
    FOR (i, a.size()) {
        p[i + 1] = p[i] + a[i];
    }   
    return p;
}
tcT> vector <T> sufsum(vector <T> &a) {
    vector <T> p(a.size() + 1);
    for (int i = (int)a.size() - 1; i >= 0; --i) {
        p[i] = p[i + 1] + a[i];
    }
    return p;
}
ll gcd(ll a, ll b) {
    while (b) {
        tie(a, b) = mp(b, a % b);
    }
    return a;
}
int Bit(int mask, int bit) { return (mask >> bit) & 1; }
signed main() {
    #ifdef LOCAL
    #else
    #define endl '\n'
    ios_base::sync_with_stdio(0); cin.tie(0);
    #endif
    int n, m;
    cin >> n >> m;
    vi a(n), b(n);cin>>a>>b;
    n++;
    a.app(0); b.app(0);

    vi c, d;
    FOR (i, n) {
        c.app((a[(i + 1)%n] - a[i]));
        d.app(b[(i + 1)%n] - b[i]);
    }

    debug2(c,d);
    vi e;
    FOR (i, n) {
        e.app(((d[i] - c[i])%m+m)%m);
    }

    sort(all(e));
    debug(e);

    int ans = 1e18;
    int tot = accumulate(all(e), 0ll);
    int L = 0;
    FOR (i, n) {
        L += e[i];
        int R = m * (sz(e) - i - 1) - (tot - L);
        debug3(i, L, R);
        ckmin(ans, max(L,R));
    }
    cout<<ans<<endl;
}