#include <regex>
#include <string>
#include <iostream>
#include <time.h>
using namespace std;

int main()
{
	struct tm tm;
    time_t t;
        string data("1\n2\n3");
        std::regex pattern("^\\d+$");
        std::smatch result;

        while (regex_search(data, result, pattern)) {
        	std::cout << result[0] << std::endl;
        	data = result.suffix().str();
		}
}