c++输入1234，输出123.124.134.234

c++输入1234，输出
123，
124，
134，
234，要如何实现呢

如果固定是输入4位数那就按我的写。

#include <iostream>

int GetOnes(int num_);
int GetTens(int num_);
int GetHundreds(int num_);
int GetThousands(int num_);

int main(void) {
    int a;
    std::cin >> a;
    std::cout << GetThousands(a) << GetHundreds(a) << GetTens(a) << ","
              << std::endl;
    std::cout << GetThousands(a) << GetHundreds(a) << GetOnes(a) << ","
              << std::endl;
    std::cout << GetThousands(a) << GetTens(a) << GetOnes(a) << ","
              << std::endl;
    std::cout << GetHundreds(a) << GetTens(a) << GetOnes(a) << "," << std::endl;
    return 0;
}

int GetOnes(int num_) {
    return num_ % 10;
}

int GetTens(int num_) {
    return num_ % 100 / 10;
}

int GetHundreds(int num_) {
    return num_ % 1000 / 100;
}

int GetThousands(int num_) {
    return num_ / 1000;
}