import java.awt.print.Printable;
import java.time.Year;
import java.util.*;


public class Main {
	
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		long A = sc.nextLong();
		long B = sc.nextLong();
		int T = sc.nextInt();
		long min = 2000000000;
		for(long i=0;i*B<=T && i<=A;i++ ) min = Math.min(min, i*B+(T-i*B+A-1)/A*A);
		
		System.out.println(min);
	}

}