#include <inttypes.h>
#include <limits.h>
#include <stdint.h>
#include <stdio.h>

/* old version:
uintmax_t isqrt(uintmax_t n){
 int i;
 for(i = 1; i <= n; i += 2) n -= i;
 return i >> 1;
}
*/

/* this version only works for unsigned types...
uintmax_t isqrt(uintmax_t n){
  uintmax_t r = 0;
  // fixed this so it should work even if uintmax_t is an odd number of bits!
  // ... i've never seen an implementation where that's the case, but i realized
  // that the code i had here before would break if someone was perverse enough
  // to do that, so i fixed it.
  for(uintmax_t i = ~(UINTMAX_MAX >> 2) & UINTMAX_MAX / 3; i; i >>= 2)
    if(n >= (i | r)){
      n -= i | r;
      r = r >> 1 | i;
    } else r >>= 1;
  return r;
}
*/

intmax_t isqrt(intmax_t n){
 if(0 > n) n = -n;
 for(intmax_t i = ((INTMAX_MAX >> 2) ^ INTMAX_MAX) / 3 << 1; i; i >>= 2)
  if(n >= (i | r)){
   n -= i | r;
   r = r >> 1 | i;
  } else r >>= 1;
 return r;
}

int main(int argc, char *argv[]){
 for(int i = 1; i < argc; ++i){
  intmax_t n = strtoimax(argv[i],NULL,0);
   printf("isqrt(%jd) == %jd%s\n", n, ISQRT(n), n < 0 ? "i" :
    "");
 }
 return 0;
}