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

int main(int argc, char ** argv) {
 if(argc < 2) printf("need input\n");
 uint32_t limit = argc < 3 ? 25000000 : strtoul(argv[2], NULL, 10);
 uint64_t input = 0;
 char * c = argv[1];
 while(*++c);
 while(c-- != argv[1]) {
  input <<= 8;
  input += *c - '0';
 }

 uint8_t * recipes = malloc(sizeof(uint8_t)*limit);
 recipes[0] = 3;
 recipes[1] = 7;
 uint32_t elf1=0, elf2=1, len=2;
 uint8_t score;
 for(int i=2;i<limit;i++) recipes[i] = 0xae;

 while (len < limit) {
  score = recipes[elf1] + recipes[elf2];
  if (score < 10) {
   recipes[len] = score;
   len += 1;
  } else {
   recipes[len]   = score/10;
   recipes[len+1] = score%10;
   len += 2;
  }
  elf1 = (elf1 + recipes[elf1] + 1) % len;
  elf2 = (elf2 + recipes[elf2] + 1) % len;
  if (((*(uint64_t*)(recipes+len-6) & 0xffffffffffff) == input)
    ||((*(uint64_t*)(recipes+len-7) & 0xffffffffffff) == input))
   break;
 }
 if (len >= limit)
  printf("Limit %d reached, try increasing (arg 2)\n", limit);
 else
  printf("%u\n", len-(score<10?6:7));
 free(recipes);
 return 0;
}