package main

import (
      "fmt"
      "strconv"
)

var sum int64 = 0

// Swap the i-th byte and j-th byte of the string
func swap(s string, i, j int) string {
      var result []byte
      for k := 0; k < len(s); k++ {
              if k == i {
                      result = append(result, s[j])
              } else if k == j {
                      result = append(result, s[i])
              } else {
                      result = append(result, s[k])
              }
      }
      return string(result)
}

// Function to find all Permutations of a given string str[i:n]
// containing all distinct characters
func permutations(str string, i, n int) {
      // base condition
      if i == n-1 {
              checkProduct(str)
              return
      }

      // process each character of the remaining string
      for j := i; j < n; j++ {
              // swap character at index i with current character
              str = swap(str, i, j)

              // recursion for string [i+1:n]
              permutations(str, i+1, n)

              // backtrack (restore the string to its original state)
              str = swap(str, i, j)
      }
}

// MxMMMM=MMMM
// MMxMMM=MMMM
func checkProduct(s string) {
      // check M x MMMM = MMMM
      m1, _ := strconv.ParseInt(s[0:1], 10, 0)
      m2, _ := strconv.ParseInt(s[1:5], 10, 0)
      prd, _ := strconv.ParseInt(s[5:9], 10, 0)
      if m1*m2 == prd {
              fmt.Printf("%d * %d = %d\n", m1, m2, prd)
              sum += prd
      }

      // check MM x MMM = MMMM
      m1, _ = strconv.ParseInt(s[0:2], 10, 0)
      m2, _ = strconv.ParseInt(s[2:5], 10, 0)
      prd, _ = strconv.ParseInt(s[5:9], 10, 0)
      if m1*m2 == prd {
              fmt.Printf("%d * %d = %d\n", m1, m2, prd)
              sum += prd
      }
}

func main() {
      str := "123456789"
      permutations(str, 0, len(str))

      fmt.Println(sum)
}