Main.cc: In function ‘int main()’: Main.cc:4:18: error: redeclaration of ‘double n’ double n,x,y,n=0; ^ Main.cc:4:12: note: ‘double n’ previously declared here double n,x,y,n=0; ^ Main.cc:6:6: error: invalid operands of types ‘double’ and ‘double’ to binary ‘operator%’ n%x-y=n; ~^~