fn sum_str(a: &str, b: &str) -> i64 {
  let ra = a.to_string().parse::<i64>();

  if let Ok(va) = ra {
    let rb = b.to_string().parse::<i64>();
  
    if let Ok(vb) = rb {
        va + vb
    } else {
        0
    }
  } else {
      0
  }
}

fn main()
{
  let a = "a123";
  let b = "456";

  println!("{} + {} = {}", a, b, sum_str(a, b))
}