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namespace base64 {
    const char* list = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
    char* get_back() {
        char* tmp = new char[256];
        for (int i = 0; i < 64; i++) tmp[list[i]] = i;
        return tmp;
    }
    string encode(const string &str) {
        string ret = "";
        for (int p = 0; p < str.length(); p += 3) {
            unsigned int tmp = ((unsigned int)((unsigned char)str[p])<<16) | ((p+1 >= str.length() ? 0 : (unsigned int)((unsigned char)str[p+1]))<<8) | (p+2 >= str.length() ? 0 : (unsigned char)str[p+2]);
            ret += list[(tmp & 16515072) >> 18];
            ret += list[(tmp & 258048) >> 12];
            ret += str.length() - p == 1 ? '=' : list[(tmp & 4032) >> 6];
            ret += str.length() - p <= 2 ? '=' : list[tmp & 63];
        }
        return ret;
    }
    string decode(const string &str) {
        const char *back = get_back();
        string ret = "";
        for (int p = 0; p < str.length(); p += 4) {
            unsigned int tmp = ((unsigned int)back[str[p]] << 18) | ((unsigned int)back[str[p+1]] << 12) | ((unsigned int)back[str[p+2]] << 6) | ((unsigned int)back[str[p+3]]);
            ret += char((tmp & 16711680) >> 16);
            if (str[p+1] != '=') ret += char((tmp & 65280) >> 8);
            if (str[p+2] != '=') ret += char(tmp & 255);
        }
        return ret;
    }
}