body {
  width: 800px;
  margin: 0 auto;
}
#graph {
  width: 640px;
  height: 250px;
  margin: 20px calc() 0 auto;
  
}
#graph2 {
  width: 640px;
  height: 250px;
  margin: 20px calc() 0 auto;
  
}
pre {
  height: 250px;
  overflow: auto;
}