using uCalcSoftware;

var uc = new uCalc();
using (var log = new uCalc.String("INFO: OK. ERROR: Fail 1. INFO: OK. ERROR: Fail 2.")) {
   
   // Find the second occurrence of "ERROR" and get everything after it.
   var remainingLog = log.StartingFrom("ERROR", 2);

   Console.WriteLine(remainingLog);
}