Go: package main

import (
    "bufio"
    "os"
    "fmt"
)

var sc = bufio.NewScanner(os.Stdin)

/**************  Cell  *****************/
type Cell struct {
    item interface{}
    next *Cell
    prev *Cell
}

func NewCell(x interface{}, ne *Cell, pr *Cell) *Cell {
    newCp := new(Cell)
    newCp.item = x
    newCp.next = ne
    newCp.prev = pr
    return newCp
}
/************  End Cell  ***************/

/**************  Queue  ****************/
type Queue struct {
    size int
    front *Cell
    rear *Cell
}

func NewQueue() *Queue {
    return new(Queue)
}

func (q *Queue) Push(x interface{}) {
    newNode := NewCell(x, nil, nil)
    if q.size == 0 {
        q.front = newNode
        q.rear = newNode
    } else {
        newNode.prev = q.rear
        q.rear.next = newNode
        q.rear = newNode
    }
    q.size++
}

func (q *Queue) PopLeft() interface{} {
    if q.size == 0 {
        return nil
    } else {
        x := q.front.item
        if q.size == 1 {
            q.front = nil
            q.rear = nil
        } else {
            q.front = q.front.next
            q.front.prev = nil
        }
        q.size--
        return x
    }
}

func (q *Queue) IsEmpty() bool {
    return q.size == 0
}

func (q *Queue) Length() int {
    return q.size
}

type State struct {
    color string
    cnt int
}

func main() {
    for {
        sc.Scan()
        init := sc.Text()
        if init == "0" {
            break
        }
        bfs(init)
    }
}

func bfs(init string) {
    dic := make(map[string]int)
    que := NewQueue()
    que.Push(State{init, 0})
    length := len(init)
    isSolved := false
    for !que.IsEmpty() {
        state := que.PopLeft().(State)
        _, ok := dic[state.color]
        if ok {
            continue
        } else {
            dic[state.color] = state.cnt
        }

        if isSingleColor(state.color) {
            fmt.Println(state.cnt)
            isSolved = true
            break
        }

        for i := 0;i < length - 1; i++ {
            color1, color2 := string(state.color[i]), string(state.color[i + 1])
            if color1 != color2 {
                color3 := other(color1, color2)
                if i <= length - 2 {
                    que.Push(State{state.color[:i] + color3 + state.color[i + 2:], state.cnt + 1})
                } else {
                    que.Push(State{state.color[:i] + color3, state.cnt + 1})
                }
            }
        }
    }
    if !isSolved {
        fmt.Println("NA")
    }
}

func other(color1, color2 string) string {
    if color1 == "r" {
        if color2 == "g" {
            return "bb"
        } else if color2 == "b" {
            return "gg"
        }
    } else if color1 == "g" {
        if color2 == "r" {
            return "bb"
        } else if color2 == "b" {
            return "rr"
        }
    } else if color1 == "b" {
        if color2 == "r" {
            return "gg"
        } else if color2 == "g" {
            return "rr"
        }
    }
    return ""
}

func isSingleColor(color string) bool {
    for _, c := range color {
        if string(c) != string(color[0]) {
            return false
        }
    }
    return true
}

C++: #include <iostream>
#include <string>
#include <map>
#include <queue>

using namespace std;


class Insect{
public:
  string body;
  int sec;
  Insect(string body, int sec): body(body), sec(sec) {}
};

bool isOneColor(string str) {
  char c = str[0];
  for(int i = 1; i < str.length(); i++) {
    if(str[i] != c) return false;
  }
  return true;
}

int main() {
  while(1) {
    string str;
    getline(cin, str);
    if(str == "0") break;

    map<string, bool> visited;
    queue<Insect> Q;
    Q.push(Insect(str, 0));
    visited[str] = true;

    int sec = -1;
    while(!Q.empty()) {
      Insect s = Q.front();
      Q.pop();
      
      if(isOneColor(s.body)) {
	sec = s.sec;
	break;
      }

      for(int i = 0; i+1 < s.body.length(); i++) {
	if(s.body[i] != s.body[i+1]) {
	  string temp = s.body;
	  if(s.body[i] != 'r' && s.body[i+1] != 'r')
	    temp[i] = temp[i+1] = 'r';
	  if(s.body[i] != 'g' && s.body[i+1] != 'g')
	    temp[i] = temp[i+1] = 'g';
	  if(s.body[i] != 'b' && s.body[i+1] != 'b')
	    temp[i] = temp[i+1] = 'b';

	  if(!visited[temp]) {
	    Q.push(Insect(temp, s.sec+1));
	    visited[temp] = true;
	  }
	}
      }
    }

    if(sec == -1) {
      cout << "NA" << endl;
    } else {
      cout << sec << endl;
    }
  }
  return 0;
}

C++: #include<cstdio>
#include<iostream>
#include<algorithm>
#include<queue>
#include<cmath>
using namespace std;
struct s{
    string worm;
    int nowans;
};
int main(){
    char dc[6][3]={'r','g','b','g','r','b','r','b','g','b','r','g','g','b','r','b','g','r'};
    while(1){
        int che[100000]={0},chenum=0;
        s IN,now;
        queue 
 que;
        cin >> IN.worm;
        IN.nowans=0;
        if(IN.worm[0]=='0')
            break;
        que.push(IN);
        while(1){
            chenum=0;
            now=que.front(),que.pop();
            for(int i=0;i<10;i++){
                if(now.worm[i]=='r')
                    chenum+=pow(3,i);
                else if(now.worm[i]=='g')
                    chenum+=pow(3,i)*2;
                else if(now.worm[i]=='b')
                    chenum+=pow(3,i)*3;
            }
            if(che[chenum])
                continue;
            else
                che[chenum]=1;
            for(int i=0;i<now.worm.size()-1;i++){
                if(now.worm[i]!=now.worm[i+1])
                    break;
                if(i==now.worm.size()-1-1){
                    printf("%d\n",now.nowans);
                    goto exit;
                }
            }
            if(now.nowans==20){
                puts("NA");
                goto exit;
            }
            for(int i=0;i<now.worm.size()-1;i++){
                if(now.worm[i]!=now.worm[i+1]){
                    for(int j=0;j<6;j++){
                        if(now.worm[i]==dc[j][0]&&now.worm[i+1]==dc[j][1]){
                            now.worm[i]=dc[j][2],now.worm[i+1]=dc[j][2],now.nowans++;
                            que.push(now);
                            now.worm[i]=dc[j][0],now.worm[i+1]=dc[j][1],now.nowans--;
                        }
                    }
                }
            }
        }
exit:
    printf("");
    }
    return 0;
}