import java.math.BigDecimal;
import java.io.*;

public class Main {
	public static void main(String args[]) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String s = br.readLine();
		
		long val[] = new long[3];
		String str[] = s.split(" ");
		for(int i = 0; i < 3; i++){
			val[i] = Long.parseLong(str[i]);
		}
		
		BigDecimal ans = new BigDecimal(1.0 * val[0] * (val[1] / 5) / val[2]);
		
		System.out.println(ans);
	}
}