#include <bits/stdc++.h>
using namespace std;
template <class T>
inline T lowbit(T n) {
  return (n ^ (n - 1)) & n;
}
template <class T>
inline int countbit(T n) {
  return (n == 0) ? 0 : (1 + countbit(n & (n - 1)));
}
template <class T>
T gcd(T a, T b) {
  return b == 0 ? a : gcd(b, a % b);
}
template <typename T>
T lcm(T a, T b) {
  return a / gcd(a, b) * b;
}
template <class T>
T my_pow(T n, T p) {
  if (p == 0) return 1;
  T x = my_pow(n, p / 2);
  x = (x * x);
  if (p & 1) x = (x * n);
  return x;
}
template <class T>
T big_mod(T n, T p, T m) {
  if (p == 0) return (T)1;
  T x = big_mod(n, p / 2, m);
  x = (x * x) % m;
  if (p & 1) x = (x * n) % m;
  return x;
}
template <class T>
inline T Mod(T n, T m) {
  return (n % m + m) % m;
}
template <class T>
T multiplication(T n, T p, T m) {
  if (p == 0) return (T)0;
  T x = multiplication(n, p / 2, m);
  x = (x + x) % m;
  if (p & 1) x = (x + n) % m;
  return x;
}
bool isVowel(char ch) {
  ch = toupper(ch);
  if (ch == 'A' || ch == 'U' || ch == 'I' || ch == 'O' || ch == 'E')
    return true;
  return false;
}
template <class T>
T extract(string s, T ret) {
  stringstream ss(s);
  ss >> ret;
  return ret;
}
template <class T>
string itos(T n) {
  ostringstream ost;
  ost << n;
  ost.flush();
  return ost.str();
}
long long stoi(string s) {
  long long r = 0;
  istringstream sin(s);
  sin >> r;
  return r;
}
double toDouble(string s) {
  double r = 0;
  istringstream sin(s);
  sin >> r;
  return r;
}
const int mod = 1e9 + 7;
long long a = 0, b = 0, d = 0, n, m, res = 0, c = 0, t = 0, ans = 0, cc = 0,
          f = 0, ff = 0, cnt = 0, cost = 0, ks = 0;
long long mn = (1e15), mx = -(1e15);
string s, ss;
int main() {
  cin >> n;
  for (__typeof(n) i = 0; i < (n); i++) {
    cin >> a;
    res += a;
    if (a > 1) res += (a - 1) * c;
    c++;
    cc = a - 1;
  }
  cout << res;
  return 0;
}
