B. ICPC Square
math; number theory
ICPC Square is a hotel provided by the ICPC Committee for the accommodation of the participants. It consists of \(N\) floors (numbered from \(1\) to \(N\)). This hotel has a very unique elevator. If a person is currently at floor \(x\), by riding the elevator once, they can go to floor \(y\) if and only if \(y\) is a multiple of \(x\) and \(y - x \leq D\).You are currently at floor \(S\). You want to go to the highest possible floor by riding the elevator zero or more times. Determine the highest floor you can reach.
A single line consisting of three integers \(N\) \(D\) \(S\) (\(2 \leq N \leq 10^{12}; 1 \leq D \leq N - 1; 1 \leq S \leq N\)).
Output a single integer representing the highest floor you can reach by riding the elevator zero or more times.
Explanation for the sample input/output #1First, ride the elevator from floor \(3\) to floor \(15\). This is possible because \(15\) is a multiple of \(3\) and \(15 - 3 \leq 35\). Then, ride the elevator from floor \(15\) to floor \(30\). This is possible because \(30\) is a multiple of \(15\) and \(30 - 15 \leq 35\). Finally, ride the elevator from floor \(30\) to floor \(60\). This is possible because \(60\) is a multiple of \(30\) and \(60 - 30 \leq 35\).