#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 7;
const int MOD = 1e9 + 7;
long long a[maxn];
int main() {
  int n;
  scanf("%d", &n);
  long long ans = 0;
  for (int i = 1; i <= n; ++i) {
    scanf("%lld", &a[i]);
    ans += a[i] * (n - a[i] + 1);
    if (i == 1) continue;
    long long t1 = a[i - 1], t2 = a[i];
    if (t1 > t2) swap(t1, t2);
    ans -= t1 * (n - t2 + 1);
  }
  printf("%lld\n", ans);
  return 0;
}
