易懂

#include <bits/stdc++.h>
using namespace std;
int main(){
int n;
double sum;
cin >> n;
if(n <= 100){
sum = n * 0.8;
}
else if(n <= 300){
sum = n * 0.9;
}
else if(n <= 500){
sum = n;
}
else{
sum = n * 1.5;
}
cout << fixed << setprecision(1) << sum;
}//搞定。