codeforce - xenia and ringroad

#include<bits/stdc++.h>
using namespace std;
#define fastread()(ios_base::sync_with_stdio(false),cin.tie(NULL));
#define ll long long
int main()
{
    int a,b;
    fastread()
    cin>>a>>b;
    int ara[b+1];
    ll ans=0;
    for(int i=0; i<b; i++)
    {
        cin>>ara[i];
        if(i==0)
        {
            if(ara[i]>=1)
            {
                ans+=ara[i]-1;
            }
            else
            {
                ans+=a+ara[i]-1;
            }
        }
        else
        {
            if(ara[i]>=ara[i-1])
            {
                ans+=ara[i]-ara[i-1];
            }
            else
            {
                ans+=a+ara[i]-ara[i-1];
            }
        }
    }
    cout<<ans<<endl;
    return 0;
}