what is wrong with this program? 3.31

what is wrong with this program? 3.31

my code is as follows but wont work:
inputStr=input('enter the number of quarters: ')
quarters=int(inputStr)
if inputStr.isdigit() :
total=total+quarters*0.25
print('Total: ', total)
else:
print('input error. ')
What is wrong with this?