// Slower C++ solution:
#include<bits/stdc++.h>

#define int long long

using namespace std;

int n,m,x,y,ans,f1[300000],f2[300000],sum;

int read(){

	char c=getchar();while (c!='-'&&(c<'0'||c>'9'))c=getchar();

	int kk=1,k=0;if (c=='-')kk=-1,c=getchar();

	while (c>='0'&&c<='9')k=k*10+c-'0',c=getchar();return kk*k;

}void putit1(int x,int y){for (;x<=200000;x+=x&(-x))f1[x]+=y;}

void putit2(int x,int y){for (;x<=200000;x+=x&(-x))f2[x]+=y;}

int findit1(int x){int ans=0;for (;x;x-=x&(-x))ans+=f1[x];return ans;}

int findit2(int x){int ans=0;for (;x;x-=x&(-x))ans+=f2[x];return ans;}

void doit(int x,int y){ 

	if (x>y){

		doit(x,m);doit(1,y);putit1(1,m-x+1),putit1(y+1,-m+x-1); 

	}else{

		putit2(x,1);putit2(y+1,-1);putit1(x,-x);putit1(y+1,x);

	}

}void doit1(int x,int y){

	if (x<y)sum+=y-x;else sum+=y+m-x;

	x=x%m+1;if (x==y)return;doit(x,y);

}

signed main(){

	n=read();m=read();x=read();ans=1e15;

	for (int i=1;i<n;i++)y=read(),doit1(x,y),x=y;

	for (int i=1;i<=m;i++)ans=min(ans,sum-findit1(i)-findit2(i)*i);

	cout<<ans<<endl;

}


// Faster C++ solution for the same problem (measured speedup: 5.125000111060397x):
#include<cstdio>

#include<algorithm>

using namespace std;

#define ll long long

const int maxn=1e5+5;

const ll INF=0x3f3f3f3f3f3f3f3f;

int a[maxn];

struct node

{

    int l,r;

    ll diff,lz;

}tree[4*maxn];

void build(int l,int r,int cur)

{

    tree[cur].l=l;

    tree[cur].r=r;

    if(l==r)

        return;

    int mid=(l+r)>>1;

    build(l,mid,cur<<1);

    build(mid+1,r,cur<<1|1);

    return;

}

void push_up(int cur)

{

    tree[cur].diff=tree[cur<<1].diff+tree[cur<<1|1].diff;

    return;

}

void push_down(int cur)

{

    if(tree[cur].lz!=0)

    {

        tree[cur<<1].diff+=(tree[cur<<1].r-tree[cur<<1].l+1)*tree[cur].lz;

        tree[cur<<1].lz+=tree[cur].lz;

        tree[cur<<1|1].diff+=(tree[cur<<1|1].r-tree[cur<<1|1].l+1)*tree[cur].lz;

        tree[cur<<1|1].lz+=tree[cur].lz;

        tree[cur].lz=0;

    }

    return;

}

void add(int l,int r,ll val,int cur)

{

    if(l>r) return;

    if(tree[cur].l>=l&&tree[cur].r<=r)

    {

        tree[cur].diff+=(tree[cur].r-tree[cur].l+1)*val;

        tree[cur].lz+=val;

        return;

    }

    if(tree[cur].l>r||tree[cur].r<l)

        return;

    push_down(cur);

    add(l,r,val,cur<<1);

    add(l,r,val,cur<<1|1);

    push_up(cur);

    return;

}

ll diff0[maxn];

void together(int cur)

{

    if(tree[cur].l==tree[cur].r)

    {

        diff0[tree[cur].l]=tree[cur].diff;

        return;

    }

    push_down(cur);

    together(cur<<1);

    together(cur<<1|1);

    push_up(cur);

    return;

}

ll minn[maxn];

int main()

{

    int n,m;

    scanf("%d%d",&n,&m);

    for(int i=1;i<=n;i++)

        scanf("%d",&a[i]);

    build(0,m-1,1);

    ll base=0;

    for(int i=1;i<n;i++)

    {

        if(a[i]<a[i+1])

        {

            base+=(ll)(a[i+1]-a[i]);

            add(a[i]+1,a[i+1]-1,-1,1);

            add(a[i+1],a[i+1],a[i+1]-a[i]-1,1);

        }

        else

        {

            base+=(ll)(m-a[i]+a[i+1]);

            add(0,0,-(m-a[i]),1);

            add(1,a[i+1]-1,-1,1);

            add(a[i+1],a[i+1],m-a[i]+a[i+1]-1,1);

            add(a[i]+1,m-1,-1,1);

        }

    }

    together(1);

    minn[0]=base;

    for(int i=1;i<=m;i++)

        minn[i]=minn[i-1]+diff0[i-1];

    ll ans=INF;

    for(int i=1;i<=m;i++)

        ans=min(ans,minn[i]);

    printf("%lld\n",ans);

    return 0;

}

/*

 4 6

 1 5 1 4

 8 9 7 5 6 9

 

 9 9 8 7 6 5 4 3 2

 */