// ex_ch6_7.c
#include <stdio.h>

int main(void)
{
	float one, two;
	printf("Input two floating point numbers (or use q to quit)\n");

	while (scanf("%f %f", &one, &two) == 2)
	{
		printf("%f\n", (one - two) / (one * two));
	}
	return 0;
}