#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;
 }

我跑出来-1，但是听说有人是255,大家都跑一下，好像不同的机子有差异，如果不一样那就是废题了