#include <iostream>
#include <stdlib.h>

using namespace std;

int main()
{
  char a[30],b[30];
  cin>>a>>b;
  if(strlen(a)!=strlen(b)) cout<<"nu";
  else
  {
      int ok=1;
      while(strcmp(a,b)!=0 && ok)
      {
          if(strchr(b,a[0])!=0)
          {
              strcpy(strchr(b,a[0]), strchr(b,a[0])+1);
              strcpy(a,a+1);
          }    
          else ok=0;
      }           
     if(ok) cout<<"da";
     else cout<<"nu";
  }    
  system("PAUSE");	
  return 0;
}