笔试题：Suggest a simple and fast way to multiply the input integer digit by 7。

#include "stdio.h"

int main(int argc, char **argv )
{
   int a;
   printf("Please Input Your Number:\n");
   scanf("%d", &a);
   printf("Before Multiplying, the number is:%d\n", a);
   int b=( (a<<3)-a );
   printf("Caculation Results is:%d.\n", b);

}