Extracting timestamp from brackets

I need to get the UNIX timestamp value wrapped in brackets like below returned from the Xero API and post it as a date. Is this possible with the split function (or any other wappler functions)?

“UpdatedDateUTC”: “/Date(1518685950940+0000)/”,

This is the line of the repeat I need to extract it from/to

apiInvoices.data.Invoices[$index].UpdatedDateUTC

This is an example from Stack Overflow, I’ve tried adjusting split to similar syntax but can’t get it to work…

string input = "User name (sales)";
string output = input.Split('(', ')')[1];

Thanks!