#include <bits/stdc++.h>
using namespace std;
bool sortbysec(pair<int, string> a, pair<int, string> b) {
  if (a.first != b.first)
    return a.first > b.first;
  else
    return a.second < b.second;
}
int binarySearch(vector<int> a, int n, int key) {
  int low = 0;
  int high = n, mid;
  while (low <= high) {
    mid = (low + high) / 2;
    if (a[mid] <= key) {
      low = mid + 1;
    } else if (a[mid] > key) {
      high = mid - 1;
    }
  }
  if (high - low == 1) {
    if (a[low] >= key)
      return low;
    else
      return high;
  } else
    return mid;
}
vector<int> SieveOfEratosthenes(int n) {
  vector<int> prime(n + 1, 1);
  for (int p = 2; p * p <= n; p++) {
    if (prime[p] == 1) {
      for (int i = p * p; i <= n; i += p) prime[i] = 0;
    }
  }
  return prime;
}
vector<pair<long long, long long>> v;
void primeFactors(long long n) {
  v.clear();
  long long k = 0;
  while (n % 2 == 0) {
    k++;
    n = n / 2;
  }
  if (k != 0) v.push_back({2, k});
  for (long long i = 3; i <= sqrt(n); i = i + 2) {
    k = 0;
    while (n % i == 0) {
      k++;
      n = n / i;
    }
    if (k != 0) v.push_back({i, k});
  }
  if (n > 2) v.push_back({n, 1});
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int t = 1;
  while (t--) {
    long long n;
    cin >> n;
    long long ans = n;
    long long a[n];
    for (int i = 0; i < n; i++) {
      cin >> a[i];
      ans += (i + 1) * (a[i] - 1);
    }
    cout << ans;
  }
}
