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