import java.util.*;

public class Main {
	public static void main (String[] args)  {
		Scanner sc = new Scanner(System.in);
		long a = sc.nextInt();
		long b = sc.nextInt();
		long t = sc.nextInt();
		long min = Long.MAX_VALUE;
		for (int i = 0; i <= a && b * i <= t; i++) {
		    long value = (t - b * i + a - 1) / a * a + b * i;
		    min = Math.min(value, min);
		}
		System.out.println(min);
	}
}