import java.util.Arrays;
import java.util.Scanner;


public class no176 {
void run() {
	Scanner sc = new Scanner(System.in);
	long A, B, T;
	A = sc.nextInt();
	B = sc.nextInt();
	T = sc.nextInt();
	long ans = Long.MAX_VALUE;
	for (int i = 0; A*i <= T+A && i <= A; i++) {
		ans = Math.min(ans, A*i + (T-A*i+B-1)/B * B);
	}
	System.out.println(ans);
}

void debug(Object... o) {
	System.out.println(Arrays.deepToString(o));
}

public static void main(String[] args) {
	new no176().run();
}
}