%{
#include <stdio.h>
%}

%option noyywrap

%%
[a-mA-M]  {return yytext[0] + 13;}
[n-zN-Z]  {return yytext[0] - 13;}
.         {return yytext[0];}
%%

int main( ) {
  /* keep reading until 0 (end of input) */
  char c = 1;
  while(c != 0) {
    c = (char) yylex( );
    printf("%c", c);
  }
  return 0;
}