Error when creating interactive map using Rshiny

Question

library(shiny)
library(dplyr)
library(ggplot2)
library(readr)
library(htmltools)
library(leaflet)    
library(geojsonio)

ui <- fluidPage(
  selectInput (inputId = "medal", label = "Choose medal", list("Gold", "Silver", "Bronze", "Total")),
  leafletOutput("Olymap"))


# Define server logic required to draw a histogram



server <- function(input, output) {
  shapeurl <- "https://raw.githubusercontent.com/johan/world.geo.json/master/countries.geo.json"
  WorldCountry <- geojson_read(shapeurl, what = "sp")
  Olympics<- read.csv("Olympics.csv")
  groupcountry <- Olympics[, c(2, 10, 11, 12, 13)]
  
  Oly_react <- reactive ({groupcountry %>%
      group_by(Country) %>%
      summarise(medalt = sum(input$medal))})
  
  CountryOly <- reactive({left_join(data.frame(Name = WorldCountry$name), Oly_react(), by = c("Name" ="Country"))})
  pat <- reactive({ CountryOly() %>% colorBin("viridis", domain = medalt)})
  Pops <- reactive({ CountryOly() %>% paste("<strong>", Name, "</strong>", "<br/>",
                                            "UrbanPop:", medalt)})
  output$Olymap <-renderLeaflet({leaflet(WorldCountry) %>% addTiles() %>%
    addPolygons(
      fillColor = pat(CountryOly$medalt),
      weight = 2,
      opacity = 1,
      color = "white",
      fillOpacity = 0.7,
      highlight = highlightOptions(
        weight = 3,
        color = "grey",
        fillOpacity = 0.7,
        bringToFront = TRUE),
      popup = Pops()) 
})
}

# Run the application
shinyApp(ui = ui, server = server)

I'm trying to create an interactive map about the Olympic medals won by each country. I want to create a dropdown menu that allows the user to select "Gold","Silver", "Bronze", or "Total" and the map will change accordingly. But whenever I run the app, it keeps showingenter image description here Error'medalt' not found and I don't really know what's going on. I would really appreciate anyone who can help me with this problem.