#include<bits/stdc++.h>
using namespace std;

int main(){
  char zu[8][9];
  string bun;
  char x='a';
  int nagasa;
  int smp1,smp2;
  for(int i=0;i<6;i++){
    for(int j=0;j<5;j++){
      zu[i][j] = x;
      x++;
    }
  }
  zu[5][1]='.';
  zu[5][2]='?';
  zu[5][3]='!';
  zu[5][4]=' ';
  cin >> bun;
  nagasa = bun.size();
  int flag=0;
  for(int i=0;i<nagasa;i=i+2){
    smp1 = bun[i]-'0'-1;
    smp2 = bun[i+1]-'0'-1;
    if(smp1 > 5 || smp2 > 4){
      flag = 1;
    }
  }
  int a = nagasa%2;
  if(a == 0 && flag == 0){
    for(int i=0;i<nagasa;i=i+2){
      smp1 = bun[i]-'0'-1;
      smp2 = bun[i+1]-'0'-1;
      cout << zu[smp1][smp2];
    }
    cout << endl;
  }
  else{
    cout << "NA" << endl;
  }
}