#include <bits/stdc++.h>
 
using namespace std;
 
#define debug cout << "I was here!" << '\n'
#define all(a) a.begin(), a.end()
 
typedef unsigned u;
typedef long long ll;
 
void solve()
{
    int n; cin >> n; 
    
    ll ans = 0;
    for (int i = 0; i < n; i++)
    {
        ll a; cin >> a;
        
        ans += ((a - 1) * i) + a;
    }
    
    cout << ans << '\n';
}
 
int main()
{
    int t = 1; //cin >> t;
    while (t--) solve();
 
    return 0;
}