public static void Main()
var testDec = Convert.ToDecimal(null);
Console.WriteLine(getExpiringPolicyNumber("S-0031-PK-7-2"));
public static string getExpiringPolicyNumber(string currentPolicyNumber) {
if(currentPolicyNumber == "" || currentPolicyNumber == null) {
string[] policyNumberParts = currentPolicyNumber.Split('-');
int renewalIndicator = Convert.ToInt16(policyNumberParts[policyNumberParts.Length - 1]);
if(renewalIndicator == 0) {
} else if(renewalIndicator > 0) {
return String.Join("-", policyNumberParts.Take(policyNumberParts.Length - 1).ToArray()) + "-" + (renewalIndicator-1);