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