markup <- function(n) {
  if ( n < 1 ) {
    return(cat("Give a positive integer, please!"))
  }
  number <- 1
  while ( number < n ) {
    cat(number, ", (", sample(colors(), size = 1), ") ...\n", sep = "")
    number <- number + 1
  }
  cat(n, ".  All done!\n", sep = "")
}

markup(6)

markup(0)

markup(1)

markupPester <- function(n) {
  valid <- function(input) {
    !is.na(input) & is.numeric(input) & input >= 1
  }
  if ( !valid(n) ) {
    repeat {
      n <- as.numeric(readline("Give a positive integer, please! "))
      if ( valid(n) ) break
    }
  }
  number <- 1
  while ( number < n ) {
    cat(number, ", (", sample(colors(), size = 1), ") ...\n", sep = "")
    number <- number + 1
  }
  cat(n, ".  All done!\n", sep = "")
}

markupPester(5)

markupPester(0)