Each digit at most twice

Write a positive integer in decimal without leading zeros. The number satisfies the rule when no digit appears three or more times. For example $20152015$ satisfies the rule, and $1000$ does not because the digit $0$ appears three times.

Given a positive integer $U$, find the largest integer $L$ with $L \le U$ that satisfies the rule. Every one-digit number satisfies the rule, so such an $L$ always exists.

The first line contains an integer $U$ ($1 \le U \le 10^{18}$).

Print the largest integer not greater than $U$ whose decimal representation has no digit appearing three or more times.