#include<stdio.h>
#include<stdlib.h>

int main(int o, char **O)
{
   FILE *x[3];
   int 
       y[4], r[4], z[4],
       C, h, i, n, a, t, s, u[2][3][4] =
   {
      {
         {6, 9, 0, 3},
         {1, 10, 4, 7},
         {5, 11, 2, 8}
      },
      {
         {3, 0, 6, 9},
         {10, 1, 4, 7},
         {8, 2, 5, 11}
      }
   },
       M, I, R, A, K, U[2], RU[2], N[2];
   float f, q[12];
   unsigned char p[2][3<<16], d[12], b[256][256];

   if( o < 4 )
      return !puts("<a.ppm> <b.ppm> <output.ppm> [odd]");
   else
   {
      for(h = 0, M = SEEK_SET; h < 2; h++)
      {
         if( !(x[h] = fopen(O[h + 1], "rb")) )
            goto e;
         fseek(x[h], 0, M);
         if( (int)fread(*b, 1, 256, x[h]) < 1 ||
             sscanf((char*)*b, *O = "P6\n%d %d\n%d\n", &U[h], &N[h], &i) - 3 ||
             i - 255 )
            goto e;
         for(i = C = RU[h] = 0; i < 256 && !RU[h]; i++)
            if( b[0][i] == '\n' )
               if( ++C == 3 )
                  fseek(x[h], RU[h] = i + 1, M);
         if( !RU[h] || U[h] < 1 || U[h] > (1<<16) )
            goto e;
      }
      if( *U - U[1] || *N - N[1] )
         goto e;

      for(h = 0; h < 256; h++)
         for(i = 0; i < 256; b[h][i++] = 0);

      for(i = 0; i < *N; i++)
      {
         for(h = 0; h < 2; h++)
            if( fread(p[h], 3**U, 1, x[h]) - 1 )
               goto e;
         for(h = 0; h < 3**U; h++)
            b[p[0][h]][p[1][h]] = 1;
      }

      *y = *r = y[2] = r[2] = 64;
      y[1] = r[1] = y[3] = r[3] = 192;
      A = (y[1] - *y) * (y[3] - y[2]);
      for(M = 64; M > 0; M /= 2)
      {
         for(t = -1; t < 1; t++)
            if( (*z = *r + t * M) > -1 )
               for(I = -1; I < 1; I++)
                  if( (z[2] = r[2] + I * M) > -1 )
                     for(s = 1; s > -1; s--)
                        if( (z[1] = r[1] + s * M) < 257 )
                           for(R = 1; R > -1; R--)
                              if( (z[3] = r[3] + R * M) < 257 )
                                 if( (K = (z[1] - *z) * (z[3] - z[2])) > A )
                                 {
                                    for(h = C = 0; h < 256 && C > -1 && C < 256; h++)
                                       for(n = h * (z[1] - z[i = 0]) / 256 + *z; i < 256 && C > -1 && C < 256; i++)
                                       {
                                          a = i * (z[3] - z[2]) / 256 + z[2];
                                          if( b[h][i] )
                                             C = (3 * n - a) / 2;
                                       }
                                    if( C > -1 && C < 256 )
                                       for(C = 0, A = K; C < 4; C++)
                                          y[C] = z[C];
                                 }
         for(C = 0; C < 4; C++)
            r[C] = y[C];
      }

      if( !(x[2] = fopen(O[3], "wb+")) )
         goto e;
      else
      {
         fprintf(x[2], *O, 2 * *U, 2 * *N, 255);

         for(h = 0; h < 2; h++)
            fseek(x[h], RU[h], SEEK_SET);
         C = o < 5 ? 1 : 0;
         for(i = 0; i < *N; i++)
         {
            for(h = 0; h < 2; h++)
               if( fread(p[h], 3 * *U, 1, x[h]) - 1 )
                  goto e;

            for(M = 0; M < 7; M += 6)
               for(h = 0; h < *U; h++)
               {
                  for(n = 0; n < 3; n++)
                  {
                     for(a = 0; a < 2; a++)
                        q[u[C][n][a]] =
                           p[a][h * 3 + n] * (r[a * 2 + 1] - r[a * 2]) / 256.f + r[a * 2];
                     q[u[C][n][2]] =
                     q[u[C][n][3]] =
                        (3 * q[*u[C][n]] - q[u[C][n][1]]) / 2;
                  }
                  for(n = 0; n < 12; d[n++] = t < 0 ? 0 : (t > 255 ? 255 : t))
                  {
                     t = q[n];
                     f = q[n] - t;
                     if( rand() < f * RAND_MAX )
                        t++;
                  }
                  fwrite(d + M, 6, 1, x[2]);
               }
         }
      }
   }

   for(h = 0; h < 3; t = fclose(x[h++]));
   return t;

e:
   return !puts("error");
}