= 求绝对值 =
http://acm.hdu.edu.cn/showproblem.php?pid=2003

{{{#!cplusplus
/*written by czk*/
#include <stdio.h>
#include <math.h>

int main() {
    double r;
    while(scanf("%lf", &r) != EOF)
        printf("%.2f\n", fabs(r));
}
}}}