103A - Testing Pants for Sadness - CodeForces Solution

#include <bits/stdc++.h>
using namespace std;
#define ll long long
int main()
{
  int n;
  cin>>n;
  ll arr[n];
  ll count=0;
  for(int i=0;i<n;i++)
  {
    cin>>arr[i];
  }
  for(int i=0;i<n;i++)
  {
    count += ((i+1)*arr[i])-i;
  }
  cout<<count;
  return 0;
}