#include <bits/stdc++.h>
using namespace std;
int n;
long long ans;
int a[150000 + 1];
int main() {
  scanf("%d", &n);
  for (register int i = 1; i <= n; ++i) {
    scanf("%d", &a[i]);
    ans += 1LL * a[i] * (n - a[i] + 1);
  }
  for (register int i = 1; i <= n; ++i)
    ans -= 1LL * min(a[i], a[i + 1]) * (n - max(a[i], a[i + 1]) + 1);
  printf("%lld", ans);
}
