fn main() {
  let _: usize = read();
  let vec: &Vec<i64> = &read_vec();
  
  let csum = vec.iter().scan(0,|a,&x|{*a+=x; Some(*a)}).sum::<i64>();
  
  let mut buf = vec![];
  let mut cd = 0;
  let mut amax = vec[0];
  for &a in vec {
    let d = std::cmp::max(0, amax - a);
    cd += d;
    buf.push(cd);
    amax = std::cmp::max(amax, a);
  }
  let cdiff = buf.iter().sum::<i64>();
  
  println!("{}", csum - cdiff);
}

fn read<T: std::str::FromStr>() -> T {
  let mut buf = String::new();
  std::io::stdin().read_line(&mut buf).ok();
  buf.trim().parse::<T>().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
  let mut buf = String::new();
  std::io::stdin().read_line(&mut buf).ok();
  buf.trim().split_whitespace().map(|t| t.parse::<T>().ok().unwrap()).collect()
}