R Shiny infinite loop

observe infinite loop

After two numbers are inputed, the program is supposed to multiply them and output in the third row of dataframe.
However, program goes to infinite loop. Also, multiplication should not truncate or round up/down the double numbers.
Please advise how to solve it. Thank you

library(shiny)
library(rhandsontable)


create_df <- function(){
GM<-data.frame(matrix(0.0, ncol = 5, nrow = 3))
col_names <- c("2015", "2016", "2017", "2018", "2019")
row_names <- c("Array1", "Array2", "Product")
colnames(GM) <- col_names
rownames(GM) <- row_names
return(GM)
}


ui <- fluidPage(
  
  
  titlePanel("GM"),
  
  mainPanel(
    rHandsontableOutput("GM"))
)





server <- function(input, output) {
  
  v = reactiveValues()
  
  observe({input$GM
    if (!is.null(input$GM)) {
      v$GM <- hot_to_r(input$GM)
      print(v$GM) # to see if values get rounded down
    } else {
      v$GM <- create_df()
    }
  })
  
  
  
  observe({
    v$GM[3,]<-v$GM[1,] * v$GM[2,]
  })
  
  output$GM <- renderRHandsontable({
    
    rhandsontable(v$GM, rowHeaderWidth = 150) %>%
      hot_col(colnames(v$GM)[1], format = "0,0.00") %>%
      hot_col(colnames(v$GM)[2], format = "0,0.00") %>%
      hot_col(colnames(v$GM)[3], format = "0,0.00") %>%
      hot_col(colnames(v$GM)[4], format = "0,0.00") %>%
      hot_col(colnames(v$GM)[5], format = "0,0.00") %>%
      hot_cols(colWidths = 100) %>%
      hot_rows(rowHeights = 30)
  })
}


shinyApp(ui = ui, server = server)