#include <stdio.h>

#include <malloc.h>

extern char **argvec;

int n0;
int n;
unsigned char *p2;
unsigned char *left;
unsigned char *sum;
unsigned char *bits;
unsigned char *num;
char *fmtbuf;
int exp2;
int exp10;
unsigned char **numlist[] = { &p2, &left, &sum, &bits, &num, 0 };

void alloc()
{
 int i;

 for (i=0;numlist[i];i++)
  { *numlist[i] = (unsigned char *) malloc(n);
  }
 fmtbuf = malloc(n+1);
}

void grownum(addl)
int addl;
{
 int i;

 for (i=0;numlist[i];i++)
  { *numlist[i] = (unsigned char *) realloc((char *)*numlist[i],n+addl);
    bzero(n+*numlist[i],addl);
  }
 fmtbuf = realloc(fmtbuf,n+addl+1);
 n += addl;
}

char *fmtnum(num)
unsigned char *num;
{
 int i;

 for (i=0;i<n;i++) fmtbuf[i] = '0' + num[i];
 fmtbuf[n] = '\0';
 return(fmtbuf);
}

void initnum(s)
char *s;
{
 int sawdot;
 int sawdigit;
 int i;

 exp10 = 0;
 i = 0;
 sawdot = 0;
 sawdigit = 0;
 for (;*s;s++)
  { if (*s == '.')
     { sawdot = 1;
       continue;
     }
    if (!sawdigit && (*s == '0'))
     { if (sawdot) exp10 --;
       continue;
     }
    if (! isdigit(*s)) continue;
    sawdigit = 1;
    if (! sawdot) exp10 ++;
    if (i < n) num[i++] = *s - '0';
  }
 for (;i<n;i++) num[i] = 0;
 printf("   initnum: %s x 10^%d\n",fmtnum(num),exp10);
}

xdiv2(np,e10p)
unsigned char **np;
int *e10p;
{
 int i;
 int j;
 int t;
 unsigned char *num;

 num = *np;
 if (num[0] < 2)
  { if (e10p) (*e10p) --;
    t = num[0];
    i = 1;
    j = 0;
  }
 else
  { t = 0;
    i = 0;
    j = 0;
  }
 if (num[n-1] & 1)
  { grownum(1);
    num = *np;
  }
 while (i < n)
  { t = (t * 10) + num[i++];
    num[j++] = t / 2;
    t %= 2;
  }
 if (j < n) num[j++] = t ? 5 : 0;
}

xmul2(np,e10p)
unsigned char **np;
int *e10p;
{
 int i;
 int j;
 int t;
 unsigned char *num;

 num = *np;
 if (num[0] > 4)
  { if (e10p) (*e10p) ++;
    if (num[n-1] % 5)
     { grownum(1);
       num = *np;
     }
    t = num[n-1] / 5;
    i = n - 1;
    j = n;
  }
 else
  { t = 0;
    i = n;
    j = n;
  }
 while (i > 0)
  { t += 2 * num[--i];
    if (t < 10)
     { num[--j] = t;
       t = 0;
     }
    else
     { num[--j] = t - 10;
       t = 1;
     }
  }
 if (j > 0)
  { num[--j] = t;
  }
 else if (t)
  { fprintf("xmul2 panic 1\n");
    abort();
  }
}

expadjust()
{
 exp2 = 0;
 while (exp10 > 0)
  { xdiv2(&num,&exp10);
    exp2 ++;
    printf(" expadjust: %s exp10=%d exp2=%d\n",fmtnum(num),exp10,exp2);
  }
 while ((exp10 < 0) || (num[0] < 5))
  { xmul2(&num,&exp10);
    exp2 --;
    printf(" expadjust: %s exp10=%d exp2=%d\n",fmtnum(num),exp10,exp2);
  }
}

tobinary()
{
 int b;
 int i;
 int t;
 int nz;

 printf("  tobinary: %s\n",fmtnum(num));
 bcopy(num,left,n);
 bzero(p2,n);
 bzero(sum,n);
 p2[0] = 5;
 b = 0;
 while (b < n0)
  { t = 1;
    for (i=0;i<n;i++)
     { if (p2[i] == left[i]) continue;
       if (p2[i] > left[i]) t = 0;
       break;
     }
    bits[b++] = t;
    if (t)
     { t = 0;
       nz = 0;
       for (i=n-1;i>=0;i--)
	{ t = left[i] - p2[i] - t;
	  if (t < 0)
	   { left[i] = t + 10;
	     t = 1;
	   }
	  else
	   { left[i] = t;
	     t = 0;
	   }
	  if (left[i]) nz = 1;
	}
       if (t)
	{ fprintf(stderr,"tobinary panic 1\n");
	  abort();
	}
       t = 0;
       for (i=n-1;i>=0;i--)
	{ t += p2[i] + sum[i];
	  if (t < 10)
	   { sum[i] = t;
	     t = 0;
	   }
	  else
	   { sum[i] = t - 10;
	     t = 1;
	   }
	}
       printf("tobinary -: %s\n",fmtnum(p2));
       printf("tobinary =: %s\n",fmtnum(left));
     }
    if (! nz) break;
    t = 0;
    for (i=0;i<n;i++)
     { t = (t * 10) + p2[i];
       p2[i] = t / 2;
       t %= 2;
     }
  }
 printf("    binary: %s\n",fmtnum(bits));
 printf("       sum: %s\n",fmtnum(sum));
}

sumadjust()
{
 int i;

 if (exp2 < 0)
  { for (i=exp2;i<0;i++)
     { xdiv2(&sum,(int *)0);
       printf(" sumadjust: %s\n",fmtnum(sum));
     }
  }
 else if (exp2 > 0)
  { for (i=exp2;i>0;i--)
     { xmul2(&sum,(int *)0);
       printf(" sumadjust: %s\n",fmtnum(sum));
     }
  }
 printf("       sum: %s\n",fmtnum(sum));
}

main(ac,av)
int ac;
char **av;
{
 if (ac != 3)
  { fprintf(stderr,"Usage: %s nbits number\n",argvec[0]);
    exit(1);
  }
 n = atoi(av[1]);
 n0 = n;
 alloc();
 initnum(av[2]);
 expadjust();
 tobinary();
 sumadjust();
 exit(0);
}