#include <bits/stdc++.h>
using namespace std;
int n, m, a[100010];
long long t;
int main() {
  cin >> n >> m;
  a[0] = 1;
  for (int i = 1; i <= m; i++) {
    cin >> a[i];
    if (a[i] > a[i - 1]) t += (a[i] - a[i - 1]);
    if (a[i] < a[i - 1]) t += (n - a[i - 1] + a[i]);
  }
  cout << t;
}
