#include <iostream>
#include <iomanip>
using namespace std;
int main(){
	float z=6*9.6;
	float zg=z-5*9.4;
	float zd=z-5*9.8;
	float p=(z-zg-zd)/4;
	cout<<setw(5)<<fixed<<setprecision(2)<<p;
	//printf("%5.2f",p);
	//cout<<" 9.60";
	return 0;
}