shinyServer(function(input, output, session) {
    session$onSessionEnded(function() shiny::stopApp())

    output$plot <- renderPlot({
        hist(faithful$eruptions, probability = TRUE, 
             breaks = as.numeric(input$n_breaks),
             xlab = "Duration (minutes)", 
             main = "Geyser eruption duration")

        dens <- density(faithful$eruptions, adjust = input$bw_adjust)
        lines(dens, col = "blue")
    })
})