#include<bits/stdc++.h> using namespace std; int main(){ int a; cin>>a; if(0<=a&&a<5) printf("%.3lf",-1*x+2.5); else if(5<=a&&a<10) printf("%.3lf",2-1.5*(x-3)*2); else if(5<=a&&a<10) printf("%.3lf",double(x)/2.0-1.5); return 0; }