C++ :

#include <iostream>
#include <cstdio>
using namespace std;
int main()
{
    double cost,ans;
    cin>>cost;
    if(cost<=8)
    {
        ans=2.5*cost;
    }
    else
    {
        ans=2.5*8+(cost-8)*4;
    }
    printf("%.1lf\n",ans);
    return 0;
}

Pascal :

var s,n:real;
BEGIN
	readln(n);
	if n<=8 then s:=n*2.5 else s:=8*2.5+(n-8)*4;
	writeln(s:0:1);
END.