//暴力枚举35pts 
#include<bits/stdc++.h>
#define ll long long
using namespace std;
int a[100005];
int main(){
	ios::sync_with_stdio(false);
	int n,m;cin>>n>>m;
	for(int i=0;i<n;i++){
		cin>>a[i];
	}
	ll mn=222147483647;
	for(int x=1;x<=m;x++){
		ll step=0;
//		cout<<"x="<<x<<endl;
		for(int i=1;i<n;i++){
			int nored,red;
			if(a[i]>=a[i-1])nored=a[i]-a[i-1];
			else nored=a[i]+m-a[i-1];
			if(a[i]>=x)red=a[i]-x+1;
			else red=a[i]+m-x+1;
//			cout<<i<<"(i):nored="<<nored<<";red="<<red<<";gongshi:"<<step<<"(step)+"<<min(nored,red)<<"(min(nored,red))=";
			step+=min(nored,red);
//			cout<<step<<endl;
		}
//		cout<<x<<"<-x step->"<<step<<"<-step min->"<<mn<<endl;
		mn=min(step,mn);
	}
	cout<<mn;
	return 0;
}