12305 - 邮寄包裹

#include<bits/stdc++.h>
using namespace std;
int main(){
  	int n;
  	double ans=0.2;
  	cin>>n;
  	if(n>30) cout<<"Fail";
  	else{
    	if(n<=10) ans+=0.8*n;
      	else if(n<=20) ans+=0.75*n;
      	else ans+=0.7*n;
      	printf("%.2lf",ans);
    }
 	return 0;
}