# Function to calculate library fine
calculate_fine <- function(days_overdue) {
  if (days_overdue <= 7) return(0) 
  if (days_overdue <= 30) return((days_overdue - 7) * 2) 
  return(50)  # Cap after 30 days
}

# Input and calculation
days_overdue <- as.integer(readline("Enter overdue days: "))
fine <- calculate_fine(days_overdue)

# Display results
cat("Fine: $", fine, "\n")
if (fine == 0) {
  cat("No fine, thank you!\n")
} else {
  if (fine == 50) cat("Fine exceeds cap. Contact library.\n")
  else cat("Please pay within the specified period.\n")
}