#include<iostream>
#include<string.h>
#include<cstdio>
#include<algorithm>
#include<stack>
#include<queue>
#include<vector>
#include<cmath>
#include<utility>
#define ll long long int
#define ld long double
#define INF 1000000000
#define EPS 0.0000000001
#define rep(i,n) for(i=0;i<n;i++)
using namespace std;
typedef pair<int, int> P;

char str[250];

int main()
{
  int i;
  char moji[6][5]={{'a','b','c','d','e'},
		   {'f','g','h','i','j'},
		   {'k','l','m','n','o'},
		   {'p','q','r','s','t'},
		   {'u','v','w','x','y'},
		   {'z','.','?','!',' '}};

  while(scanf("%s",str)!=EOF){
    if(strlen(str)%2){
      cout<<"NA"<<endl;
      continue;
    }
    rep(i,strlen(str)/2){
      //      printf("str[%d]=%d\n",2*i,str[2*i]-'0');
      //      printf("moji[%d][%d]=%c\n",str[2*i]-'0',str[2*i+1]-'0',moji[str[2*i]-'0'][str[2*i+1]-'0']);
      cout<<moji[str[2*i]-'1'][str[2*i+1]-'1'];
    }
    cout<<endl;
  }

}