can now try to run again this time we do not get pop-up syntax error window this means the interpreter did not find any errors reading the program many errors are only found when running the programso execution starts in the shellleading to run-time error the program first prompts for numberand enter we see red error traceback we will discuss its various parts it shows the program line in this little short programit is easy to go back to the python source and locate the line idle also gives you help with this in generalthe next screen shows me right-clicking the mouse (or control-click on macon top of the red "line "where it is saying the error is this generates pop-up window the only allowed option is to select go to file/line and then the focus jumps to the window with the source codeand highlights the desired lineso we have the line with the execution error we still need to figure out what is going on the bottom line of the red traceback gave description of the errortypeerrorcan only concatenate str (not "int"to str think you could start by considering the implications of "concatenate"orsince it is type erroryou could look for the types it refers to let us start by looking at the types it refers to an int clearly we have there is something about string the other data is what is its typeof course the prompt in the previous line asks for numberbut what type is returned by the input functionalways stringlook at the expression again stringplus-signand number plus-sign after string means concatenationnot numeric addition as the error saysyou can only concatenate onto the first string with another stringnot an int we want numeric additionso we need two numbersand the string must be explicitly converted you might need to look that upbut you have an idea what you are looking forwe can use int as function to convert the string we do not need to add an extra line we can make start off as an intchanging the first line to using error messages