package main

import (
  "bufio"
  "fmt"
  "os"
  "strconv"
  "sort"
  "strings"
  _ "math"
)

func main() {
  scanner := bufio.NewScanner(os.Stdin)
  hold := []int{}
  for scanner.Scan() {
     for _, num_s := range strings.Split(scanner.Text(), " ") {
     num, _ := strconv.Atoi(num_s)
      hold = append(hold, num)
    }
    break
  }
  nums := hold
  sort.Ints(nums)
  head, tail := nums[0], nums[1]
  if head == 4 && tail == 7 {
    fmt.Println(head)
    os.Exit(0)
  }
  fmt.Println(tail)
}