161: Mainline

The layout of nested if statements is a matter of convention. Here is another common arrangement:

#include  
main ( ) { 
  int ratio; 
  scanf ("%i", &ratio); 
  if (ratio < 10) 
    printf ("It is cheap!\n"); 
  else if (ratio > 30) 
    printf ("It is expensive!\n"); 
} 

Whatever convention you use, you should be able to defend it on the ground that you think it contributes to program clarity.