#include <iostream>


#include <string>


using namespace std;





char base [64] ;


char table [256] ;





void init ()


{


	for (int i=0; i < 26; i++) base[i] = 'A' + i;


	for (int i=0; i < 26; i++) base[26 + i] = 'a' + i;


	for (int i=0; i < 10; i++) base[52 + i] = '0' + i;


	base [62] = '+', base[63] = '/';


	


	for (int i = 0; i < 256; i++) table[i] = 0xff;


	for (int i = 0; i < 64; i++) table[base[i]]= i;


	table ['='] =0;	


}





string encode (string str)


{


	string ret;


	int i;


	for (i=0; i + 3 <= str.size(); i+=3){		


		ret +=base [str [i] >> 2] ;


		ret +=base [ (str [i] &0x03) <<4|str[i+1]>> 4];


		ret +=base [ (str [i +1] &0x0f) <<2|str[i+2]>> 6];


		ret += base [str [i+2] & 0x3f] ;


	}


	if (i < str.size()){


		ret +=base [str [i] >> 2];


		if (i+1==str.size () ) {			


			ret +=base [ (str [i] &0x03) <<4];


			ret +="==";


		}


		else{		


			ret += base [ (str [i] & 0x03) <<4|str[i+1] >> 4];


			ret += base [ (str [i +1] & 0x0f) << 2];


			ret +="=";


		}


	}


	return ret;


}





string decode (string str)


{


	string ret;


	int i;	


	for (i=0; i < str.size(); i +=4){


	ret +=table [str [i] ] <<2|table[str[i+1]]>>4;


	if (str[i + 2] != '=')


		ret += (table[str[i+1]]& 0x0f) << 4|table[str[i+2]] >> 2;


	if (str[i+3] != '=')


		ret += table [str [i + 2] ] << 6|table[str[i +3]];


	}


	return ret;


}





int main ()


{


	init () ;


	cout << int(table[0])<< endl;


	int opt;


	string str;


	cin >> opt >> str;


	cout << (opt ? decode(str) : encode(str))<< endl;


	return 0;


}

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