读取两个浮点数并打印它们的差值除以乘积的值

#include <stdio.h>  
int main( void )  
{  
    double n, m;  
    double res;  

    printf("Enter a pair of numbers: ");  

    while (scanf("%lf %lf", &n, &m) == 2)  
    {  
        res = (n - m) / (n * m);  
        printf("(%.3g - %.3g)/(%.3g*%.3g) = %.5g/n", n, m, n, m, res);  
        printf("Enter next pair (non-numeric to quit): ");  
    }  
    return 0;  
}