#include <bits/stdc++.h>
using namespace std;
long long ar[100005];
long long N;
int main() {
  cin >> N;
  for (long long i = 0; i < N; i++) cin >> ar[i];
  long long ans = 0ll;
  for (long long i = 0; i < N; i++) {
    long long lft = (i == 0 ? 0 : ar[i - 1]);
    if (ar[i] < lft) ans += (ar[i]) * (lft - ar[i]);
    if (ar[i] > lft) ans += (ar[i] - lft) * (N - ar[i] + 1);
  }
  cout << ans << endl;
  return (0);
}
