문제 출처 https://www.acmicpc.net/problem/16953 16953번: A → B 첫째 줄에 A, B (1 ≤ A b && num == 10000) return -1; else if (a > b) return num; else if (a == b) num = min(num, cnt); dfs(a*2, b, cnt+1); dfs(a*10+1, b, cnt+1..