AtCoder Beginner Contest 106
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Problem Statement
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Mr. Infinity has a string $S$ consisting of digits from 1 to 9. Each time the date changes, this string changes as follows:
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- Each occurrence of
2in$S$is replaced with22. Similarly, each3becomes333,4becomes4444,5becomes55555,6becomes666666,7becomes7777777,8becomes88888888and9becomes999999999.1remains as1.
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For example, if $S$ is 1324, it becomes 1333224444 the next day, and it becomes 133333333322224444444444444444 the day after next. You are interested in what the string looks like after $5 \times 10^{15}$ days. What is the $K$-th character from the left in the string after $5 \times 10^{15}$ days?
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Constraints
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$S$is a string of length between$1$and$100$(inclusive).$K$is an integer between$1$and$10^{18}$(inclusive).- The length of the string after
$5 \times 10^{15}$days is at least$K$.
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Input
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Input is given from Standard Input in the following format:
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S
K
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Output
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Print the $K$-th character from the left in Mr. Infinity's string after $5 \times 10^{15}$ days.
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样例
Input #1
1214
4
Output #1
2
The string $S$ changes as follows:
- Now: `1214`
- After one day: `12214444`
- After two days: `1222214444444444444444`
- After three days: `12222222214444444444444444444444444444444444444444444444444444444444444444`
The first five characters in the string after $5 \times 10^{15}$ days is `12222`. As $K=4$, we should print the fourth character, `2`.
Input #2
3
157
Output #2
3
The initial string is `3`. The string after $5 \times 10^{15}$ days consists only of `3`.
Input #3
299792458
9460730472580800
Output #3
2
题目信息
题面与样例版权归 AtCoder 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。