#include <bits/stdc++.h>
int main(void) {
  char str[256] = {0};
  int i, j;
  int len;
  int flag = 0;
  while (scanf("%s", str) != EOF) {
    len = strlen(str);
    if (len % 2 == 1) {
      printf("NA\n");
      continue;
    }
    j = 0;
    while (str[j] != '\0') {
      if (str[j] > 54 || str[j + 1] > 53) {
        flag = 1;
        printf("NA\n");
        break;
      }
      j = j + 2;
    }
    if (flag == 1) {
      flag = 0;
      continue;
    } else {
      i = 0;
      while (str[i] != '\0') {
        if (str[i] == '1') {
          if (str[i + 1] == '1') {
            printf("a");
            i = i + 2;
          } else if (str[i + 1] == '2') {
            printf("b");
            i = i + 2;
          } else if (str[i + 1] == '3') {
            printf("c");
            i = i + 2;
          } else if (str[i + 1] == '4') {
            printf("d");
            i = i + 2;
          } else if (str[i + 1] == '5') {
            printf("e");
            i = i + 2;
          } else {
            printf("NA");
            break;
          }
        }
        if (str[i] == '2') {
          if (str[i + 1] == '1') {
            printf("f");
            i = i + 2;
          } else if (str[i + 1] == '2') {
            printf("g");
            i = i + 2;
          } else if (str[i + 1] == '3') {
            printf("h");
            i = i + 2;
          } else if (str[i + 1] == '4') {
            printf("i");
            i = i + 2;
          } else if (str[i + 1] == '5') {
            printf("j");
            i = i + 2;
          } else {
            printf("NA");
            break;
          }
        }
        if (str[i] == '3') {
          if (str[i + 1] == '1') {
            printf("k");
            i = i + 2;
          } else if (str[i + 1] == '2') {
            printf("l");
            i = i + 2;
          } else if (str[i + 1] == '3') {
            printf("m");
            i = i + 2;
          } else if (str[i + 1] == '4') {
            printf("n");
            i = i + 2;
          } else if (str[i + 1] == '5') {
            printf("o");
            i = i + 2;
          } else {
            printf("NA");
            break;
          }
        }
        if (str[i] == '4') {
          if (str[i + 1] == '1') {
            printf("p");
            i = i + 2;
          } else if (str[i + 1] == '2') {
            printf("q");
            i = i + 2;
          } else if (str[i + 1] == '3') {
            printf("r");
            i = i + 2;
          } else if (str[i + 1] == '4') {
            printf("s");
            i = i + 2;
          } else if (str[i + 1] == '5') {
            printf("t");
            i = i + 2;
          } else {
            printf("NA");
            break;
          }
        }
        if (str[i] == '5') {
          if (str[i + 1] == '1') {
            printf("u");
            i = i + 2;
          } else if (str[i + 1] == '2') {
            printf("v");
            i = i + 2;
          } else if (str[i + 1] == '3') {
            printf("w");
            i = i + 2;
          } else if (str[i + 1] == '4') {
            printf("x");
            i = i + 2;
          } else if (str[i + 1] == '5') {
            printf("y");
            i = i + 2;
          } else {
            printf("NA");
            break;
          }
        }
        if (str[i] == '6') {
          if (str[i + 1] == '1') {
            printf("z");
            i = i + 2;
          } else if (str[i + 1] == '2') {
            printf(".");
            i = i + 2;
          } else if (str[i + 1] == '3') {
            printf("?");
            i = i + 2;
          } else if (str[i + 1] == '4') {
            printf("!");
            i = i + 2;
          } else if (str[i + 1] == '5') {
            printf(" ");
            i = i + 2;
          } else {
            printf("NA");
            break;
          }
        }
      }
      printf("\n");
    }
  }
  return 0;
}
