#include <stdio.h>
int main()
{
    float val;
    int month,date;
    int i = 0;
    scanf("%f %d %d %d",&val,&month,&date,&i);
    if(month == date )
    {
        if(month % 2 ==0 && date % 2 ==0)
        {
            if(i==1)
            {
                val = (val * 0.8)-50;
                if(val<=0)
               {
                 printf("0.00\n");
               }
               else
               {
                 printf("%.2f\n",val);
               }
            }
            else 
            {
                val = val * 0.8;
                printf("%.2f\n",val);
            }
        }
        else if(month % 2 !=0 && date % 2 !=0 )
        {
            if(i==1)
            {
                val = (val * 0.7)-50;
               if(val<=0)
               {
                 printf("0.00\n");
               }
               else
               {
                 printf("%.2f\n",val);
               }
            }
            else 
            {
                val = val * 0.7;
                printf("%.2f\n",val);
            }
        }
    }
    return 0;
}