import console;

print("Mark: ");
double mark = readDouble();
double lowest = mark;
while (mark >= 0.0) {
   if (mark < lowest) {
      lowest = mark;
   } else {
   }
   print("Mark: ");
   mark = readDouble();
}
if (lowest >= 0.0) {
   println("Lowest = " + lowest);
} else {
   println("No marks.");
}