Make sure that you have all warnings turned on when you compile your program, then the compiler will tell what might be wrong:
$ gcc -Wall a.c
a.c: In function `main':
a.c:6: warning: unknown conversion type character `.' in format
a.c:6: warning: too many arguments for format
a.c:7: warning: control reaches end of non-void function
Try:
Qt Code: 
  1. scanf("%lf", &iiput);
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