Problem:
Score : 400 points

Problem Statement

Mr. Takahashi has a string s consisting of lowercase English letters.
He repeats the following operation on s exactly K times.

Choose an arbitrary letter on s and change that letter to the next alphabet. Note that the next letter of z is a.

For example, if you perform an operation for the second letter on aaz, aaz becomes abz.
If you then perform an operation for the third letter on abz, abz becomes aba.

Mr. Takahashi wants to have the lexicographically smallest string after performing exactly K operations on s.
Find the such string.

Constraints

1≤|s|≤10^5

All letters in s are lowercase English letters.

1≤K≤10^9

Input

The input is given from Standard Input in the following format:

s
K

Output

Print the lexicographically smallest string after performing exactly K operations on s.

Sample Input 1

xyz
4

Sample Output 1

aya

For example, you can perform the following operations: xyz, yyz, zyz, ayz, aya.

Sample Input 2

a
25

Sample Output 2

z

You have to perform exactly K operations.

Sample Input 3

codefestival
100

Sample Output 3

aaaafeaaivap

Solution in Go (1.6) (judge verdict: Wrong Answer)

package main

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



func main() {
    var s string
    var k int
    fmt.Scan(&s,&k)
    n := len(s)
    a := make([]byte, n)
    for i:=0;i<n;i++{
        a[i] = s[i]
    }
    for i:=0;i<n;i++{
        if k >= int( 'z' - a[i] ) + 1 {
            k -= int( 'z' - a[i] ) + 1
            a[i] = 'a'
        }
    }
    a[n-1] += byte( k % 26 )
    for i:=0;i<n;i++{
        fmt.Printf("%c",a[i])
    }
    fmt.Printf("\n")
}





// Pairsort
type Pair struct {
    first,second int
}

type By func(p1, p2 *Pair) bool

func (by By) Sort(pairs []Pair) {
    ps := &pairSorter{
            pairs : pairs,
            by: by,
    }
    sort.Sort(ps)
}

type pairSorter struct {
    pairs []Pair
    by func(p1, p2 *Pair) bool
}

func (s *pairSorter) Len() int {
    return len(s.pairs)
}

func (s *pairSorter) Swap(i, j int) {
    s.pairs[i], s.pairs[j] = s.pairs[j], s.pairs[i]
}

func (s *pairSorter) Less(i, j int) bool {
    return s.by(&s.pairs[i], &s.pairs[j])
}

func first (p1, p2 *Pair) bool {
        return p1.first < p2.first
}

func second (p1, p2 *Pair) bool {
        return p1.second < p2.second
}
// end

func scanPairs(len int) []Pair{
    Pairs := make([]Pair, len)
    for i:=0; i<len; i++{
        fmt.Scan(&Pairs[i].first,&Pairs[i].second)
    }
    return Pairs
}



func abs32(a int) int {
    if a<0{
        return -a
    }
    return a
}

func abs64(a int64) int64 {
    if a<0{
        return -a
    }
    return a
}

func min32(a, b int) int {
    if a >= b {
        return b
    }
    return a
}

func max32(a, b int) int {
    if a >= b {
        return a
    }
    return b
}

func min64(a, b int64) int64 {
    if a >= b {
        return b
    }
    return a
}

func max64(a, b int64) int64 {
    if a >= b {
        return a
    }
    return b
}

func gcd64(a, b int64) int64 {
    if a % b == 0 {
        return b
    } else {
        return gcd64(b, a%b)
    }
}

func lcm64(a, b int64) int64 {
    return a / gcd64(a, b) * b
}

// 入力処理
var sc = bufio.NewScanner(os.Stdin)
func nextLine() string {
    sc.Scan()
    return sc.Text()
}
func nextInt() int {
    sc.Scan()
    i, e := strconv.Atoi(sc.Text())
    if e != nil {
        panic(e)
    }
    return i
}

func readLineNums(len int) (nums []int){
    for i:=0; i<len; i++{
        tmp,_ := strconv.Atoi(nextLine())
        nums = append(nums,tmp)
    }
    return
}

func readLineNums64(len int) (nums []int64){
    var num int64
    for i:=0; i<len; i++{
        tmp,_ := strconv.Atoi(nextLine())
        num = int64(tmp)
        nums = append(nums,num)
    }
    return
}

func readOneLineNums(len int) []int{
    nums := make([]int, 0, len+10)
    var num int
    sc.Split(bufio.ScanWords)
    for i:=0; i<len; i++{
        num = nextInt()
        nums = append(nums,num)
    }
    return nums
}

func scanNums(len int) []int{
    nums := make([]int, 0, len+10)
    var num int
    for i:=0; i<len; i++{
        fmt.Scan(&num)
        nums = append(nums,num)
    }
    return nums
}

func scanNums64(len int) []int64{
    nums := make([]int64, 0, len+10)
    var num int64
    for i:=0; i<len; i++{
        fmt.Scan(&num)
        nums = append(nums,num)
    }
    return nums
}

func scanString(len int) (str []string){
    var s string
    for i:=0; i<len; i++{
        fmt.Scan(&s)
        str = append(str,s)
    }
    return
}

func makeTwoNums(n,m int) ([][]int){
    Nums := make([][]int, n)
    for i:=0; i<n; i++{
        Nums[i] = make([]int, m)
    }
    return Nums
}

func sortString(s string) string{
    t := strings.Split(s, "")
    sort.Strings(t)
    return strings.Join(t, "")
}

func reverseString(s string) string{
    t := []rune(s)
    for i,j := 0, len(s)-1 ; i < j ; i, j = i+1, j-1 {
        t[i], t[j] = t[j], t[i]
    }
    return string(t)
}

func stringRev(s []byte,l int,r int) []byte{
    for i:=0;i<(r-l+1)/2;i++{
        s[l-1+i], s[r-1-i] = s[r-1-i], s[l-1+i]
    }
    return s
}

func inside(h,w,H,W int) bool{
    if h>=0 && h<H && w>=0 && w<W{
        return true
    }
    return false
}