* {
  box-sizing: border-box;
}
body {
  font-family: "Trebuchet MS", "Lucida Sans Unicode", sans-serif;
  margin: 0;
}
section {
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
}
section:first-child {
  background-color: #aaa;
}
section:nth-child(2) {
  background-color: #bbb;
}
section:nth-child(3) {
  background-color: #ccc;
}
section:last-of-type {
  background-color: #eee;
}
.nums {
  width: 400px;
  display: flex;
}
.nums .num {
  flex: 1;
  text-align: center;
  font-size: 40px;
  padding: 20px;
}