#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 1000000000000000001


int main(){
	
	long long n,m;
	cin>>n>>m;
	vector<long long> a(n),b(n);
	rep(i,n)scanf("%lld",&a[i]);
	rep(i,n)scanf("%lld",&b[i]);
	
	rep(i,n){
		a[i] -= b[i];
		a[i] += m;
		a[i] %= m;
	}
	a.insert(a.begin(),0LL);
	a.push_back(0);
	vector<long long> dp(40,Inf64);
	dp[dp.size()/2] = 0;
	for(int i=1;i<a.size();i++){
		vector<long long> ndp(40,Inf64);
		rep(j,dp.size()){
			long long x = a[i-1];
			x -= m;
			x += m*j;
			rep(k,dp.size()){
				long long y = a[i];
				y -= m;
				y += m*k;
				ndp[k] = min(ndp[k],dp[j] + abs(x-y));
			}
		}
		swap(dp,ndp);
	}
	long long ans = dp[dp.size()/2];
	cout<<ans/2<<endl;
	return 0;
}