>>52
The sqrt of its own name? If you really want that...

#include <math.h>
#include <stdio.h>
#include <inttypes.h>
main(int argc, char **argv) {
 printf("%.0Lf\n",floorl(sqrtl((long double)strtoimax(argv[0], NULL, 0))));
}

I'm assuming sqrtl() uses the h/w instruction, which should run in constant time on any CPU made since the early 90s.