Addition, subtraction of decimal value with add activity in uipath

Please help me for below script.
I have a string variable a = “-0.5”.
and use add activity :- property (right - a, left -1) [1 + a]
Please help me to add or subtract decimal value in uipath

Main.xaml (5.8 KB)

Hi @sams

try this.
cpp.xaml (6.1 KB)

thank you.