#include <iostream>
#include <string>
#include <sstream>
int main() {
std::string str;
std::cout << "Enter string: ";
std::getline(std::cin, str);
std::stringstream s(str);
std::string tmp, res;
int count = 0;
while(s >> tmp) {
res += tmp + ' ';
++count;
if(count%3==0) res += tmp + ' ';
}
res = res.substr(0, res.length()-1);
std::cout<<res;
return 0;
}