题解

代码如下

#include<bits/stdc++.h>
using namespace std;
double v,g,m,n,sum=0;
int main()
{
cin>>v>>g>>m>>n;
double pay=v*0.5;
if (g<300) sum=m;
else sum=n;
if (pay<sum) printf ("%.1lf",pay);
else printf ("%.1lf",sum);
return 0;
}