int largest_unit = 0; // 最大单位
std::string first_part;
std::string second_part;
if (len > 1 and len <= 2) {
largest_unit = 1;
} else if (len > 2 and len <= 3) {
largest_unit = 2;
} else if (len > 3 and len <= 4) {
largest_unit = 3;
} else if (len > 4 and len <= 8) {
largest_unit = 4;
} else if (len > 8) {
largest_unit = 8;
}
int largest_unit = 0; // 最大单位
std::string first_part;
std::string second_part;