题解

#include<bits/stdc++.h>
using namespace std;
int main(){
    double n;
    cin>>n;
    if(n<=17) printf("%.1lf",n*3.4);
    else if(n<=30) printf("%.1lf",17*3.4+(n-17)*5.32);
    else printf("%.1lf",(n-30)*7+17*3.4+(30-17)*5.32);
    return 0;
}