#include <stdio.h>

#define COIN 5

int main(void)
{
	unsigned long yen;
	unsigned long mg;
	unsigned long vol;
	double density;

	scanf("%lu %lu %lu", &yen, &mg, &vol);

	density = (double)((yen/COIN)*mg)/vol;

	printf("%.12f\n", density);

	return 0;
}