// program to double the value of given floating point number  and read and display that number thorugh getchar() and putchar()
// compile this program with gcc -lm programname.c      becuase it uses math.h library

#include<stdio.h>
#include<math.h>
int main()
{

	char c[20],dc[20],ch; // c store given floating value and dc stores doubled floating value in character format
	int i,k;
	int d1,d2,count1=0,count2=0,strl;

	printf("enter the floating point number");
	
	i=0;
	while((ch=getchar())!='\n')
	{
		c[i++]=ch;
	}

	c[i]='\0';
	
	i=0;
	strl=0;								// finding how many numbers are there after decimal point
	while(c[i]!='.' &&  c[i]!='\0')
	{
		i++;
		strl++;
	}	
	strl++;
	if(c[i]!='\0')
	{
	
		while(c[++i]!='\0')
		{
			count1++;
			strl++;
		}
		
	}
	
	// store this input characters as an integer in d1
	count2=0;
	d1=0;

	if(count1==0)
	strl--;

	for(i=strl-1;i>=0;i--)
	{
		if(c[i]!= '.' && c[i]!='-')
		{
			d1=d1+(c[i]-'0')*pow(10,count2++);	
		}

	}
	
	//double the value
	d2=d1*2;
	
	// store the values in array as characters in reverse order
	strl=0;	
	
	if(count1!=0)
	{
		dc[count1]='.';
		strl++;
	}
	
	for(i=0;d2!=0;i++)
	{
		if(i!=count1 || count1==0)
		{
			strl++;
			k=d2%10;

			dc[i]=k+48;
			d2=d2/10;	
		}
		

	}
	if(c[0]=='-')
	{
		dc[i++]='-';
		strl++;
	}
	dc[i]='\0';
	
	putchar('\n');
	// display using putchar
	for(i=strl-1;i>=0;i--)
	putchar(dc[i]);
	
	return 0;
}