#include <bits/stdc++.h>

using namespace std;

int n, a[100002];
long long ans = 0;

int main()
{
  cin >> n;
  for (int i = 1; i <= n; i++)
    cin >> a[i];
  for (int i = 1; i <= n; i++) {
    if (a[i] > a[i - 1])
      ans += 1ll * (a[i] - a[i - 1]) * (n - a[i] + 1);
    else {
      ans += 1ll * a[i] * (a[i - 1] - a[i]);
    }
  }
  cout << ans;
  return 0;
}