import java.io.* ;
public class doit {
   public static void main(String[] args) throws Exception {
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in)) ;
      while (true) {
         String[] f = br.readLine().split(" ") ;
         int np = Integer.parseInt(f[0]) ;
         int nm = Integer.parseInt(f[1]) ;
         int n0 = Integer.parseInt(f[2]) ;
         int r = Integer.parseInt(f[3]) ;
         if (np + nm + n0 + r == 0)
            break ;
         int rr = Integer.MAX_VALUE ;
         for (int nd=0; nd<=100; nd++) {
            int t0 = (100 + r - 1) / r ;
            int tp, tm ;
            if (nd * (r + 2) >= 100)
               tp = (100 + (r + 2) - 1) / (r + 2) ;
            else
               tp = nd + (100 - nd * (r + 2) + r - 1) / r ;
            if (nd * (r - 1) >= 100)
               tm = (100 + (r - 1) - 1) / (r - 1) ;
            else
               tm = nd + (100 - nd * (r - 1) + r - 1) / r ;
            int t = np * tp + n0 * t0 + nm * tm ;
            rr = Math.min(rr, t) ;
         }
         System.out.println(rr) ;
      }
   }
}