#include<stdio.h>
#include<conio.h>

void main()
{
	float a,b;
	char c;
		a=b=12.5;
		while(b>1.0)
		{
		printf("\nEnter a or b or c\n");
		b/=2;
			if((c=getche())=='c')	//Input a,a,b,a
				break;
			else if (c=='a')
				a+=b;
			     else a-=b;
		     }
	printf("\nThe number is %f", a);
   }