typedef unsigned int I;
static int xx = 0, xy = 0;
I mul (I ier, I icand, I mod){
  I q = 1, ac = 0;
  ier %= mod;
  icand %= mod;
  while(q <= ier) q <<= 1; // ier might be too big for this.
  while(q >>= 1) {ac <<= 1; if (q & ier) ac += icand;
     while(ac >= mod) {ac -= mod; ++xx;} ++xy;}
  return ac;}

#include <stdio.h>
int main(){int m = 72; while(--m) {
  {int j = 55; while(j--) {int k=42; while(k--) if(j*k%m != mul(j, k, m))
  printf("i = %d, j = %d, m = %d, i*j%%m = %d, mul(i, j, m) = %d\n",
          j, k, m, j*k%m, mul(j, k, m));}}}
  printf("%d reductions in %d steps\n", xx, xy);
  return 0;}

// Yields: 271227 reductions in 609336 steps