C语言菜鸟一个，有哪个大佬可以帮帮我？

#include<stdio.h>

int main()
{
	double a, b;
	char ch;
	printf("Type a pression:");
	scanf_s("%lf %c%lf", &a, &ch, &b);
	switch (ch)
	{
	case '+':
		printf("=%.2f\n",a+b); 
		break;
	case '-':
		printf("=%.2f\n",a-b); 
		break;
	case '*':
		printf("=%.2f\n",a*b); 
		break;
	case '/':
		printf("=%.2f\n",a/b);
		break;

	default:
		break;
	}
	return 0;
}

第8行改成下面的

scanf_s("%lf %c%lf", &a, &ch, 1, &b);