markov_bigrams.c

main() {
  char c = getchar(), t, p = -1;
  int freq[128] = {0};
  
  while ( (t = getchar()) != '\n' ) {
    if (p == c)
      freq[t] ++;
    p = t;
  }

  for (t=0; t<127; t++)
    if (freq[t] > freq[c])
      c = t;

  putchar(c);
  return 0;
}