#include <bits/stdc++.h>
using namespace std;
const long long maxx = 10 + 7;
const long long maxn = 1000 + 7;
const long long mod = 1e9 + 7;
const long long maxs = 5 * (1E5) + 7;
const long long maxm = 30 + 7;
const long long maxk = 1008 + 7;
const long long maxw = 100 + 7;
const long long maxh = 100 + 7;
const double pi = acos(-1.00000);
const long long ten = 10;
const double oo = 1e18 + 7;
const double eps = 1e-8;
ostream &operator<<(ostream &os, pair<int, int> &rhs) {
  os << rhs.first << " " << rhs.second << endl;
  return os;
}
istream &operator>>(istream &is, pair<int, int> &rhs) {
  is >> rhs.first >> rhs.second;
  return is;
}
istream &operator>>(istream &is, pair<long long, long long> &rhs) {
  is >> rhs.first >> rhs.second;
  return is;
}
template <class T>
T min3(T a, T b, T c) {
  return min(min(a, b), c);
}
template <class T>
T max3(T a, T b, T c) {
  return max(max(a, b), c);
}
long long qw(long long a, long long b) {
  long long ans = 1;
  while (b) {
    if (b & 1) {
      ans = ans % mod * a % mod;
      ans %= mod;
    }
    b >>= 1;
    a = a % mod * a % mod;
    a %= mod;
  }
  ans %= mod;
  return ans;
}
vector<long long> a;
long long n;
void solve() {
  cin >> n;
  a.resize(n + 2);
  a[0] = 0;
  a[n + 1] = 0;
  long long ans = 0;
  for (long long i = (1); i <= (n); i++) {
    cin >> a[i];
    if (a[i] > a[i - 1])
      ans += (a[i] - a[i - 1]) * (n - a[i] + 1);
    else if (a[i] < a[i - 1])
      ans += (a[i - 1] - a[i]) * a[i];
  }
  for (long long i = (1); i <= (n); i++) {
    if (a[i] > a[i + 1])
      ans += (a[i] - a[i + 1]) * (n - a[i] + 1);
    else if (a[i] < a[i + 1])
      ans += (a[i + 1] - a[i]) * a[i];
  }
  cout << ans / 2 << endl;
}
int main(void) {
  solve();
  return 0;
}
