http://acm.hdu.edu.cn/showproblem.php?pid=2003
1 /*written by czk*/ 2 #include <stdio.h> 3 #include <math.h> 4 5 int main() { 6 double r; 7 while(scanf("%lf", &r) != EOF) 8 printf("%.2f\n", fabs(r)); 9 }