Assume `"#"` is like a backspace in string. This means that string `"a#bc#d"` actually is `"bd"`

Your task is to process a string with `"#"` symbols.


## Examples

```
"abc#d##c"      ==>  "ac"
"abc##d######"  ==>  ""
"#######"       ==>  ""
""              ==>  ""
```