#include <iostream>
using namespace std;
int main() {
// your code goes here
int n,m;
cin>>n>>m;
int a[m];
for(int i=0;i<m;i++)
cin>>a[i];
int res=a[0]-1;
for(int i=1;i<m;i++)
{
if(a[i]>=a[i-1])
res+=a[i]-a[i-1];
else
res+=a[i]+(n-a[i-1]);
}
cout<<res<<endl;
return 0;
}
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