#include <sstream>
#include <iostream>

// copied from StackOverflow: https://stackoverflow.com/a/34403537

class AtomicWriter {
    std::ostringstream st;
    std::ostream &stream;
public:
    AtomicWriter(std::ostream &s=std::cout):stream(s) { }
    template <typename T>
    AtomicWriter& operator<<(T const& t) {
	st << t;
	return *this;
    }
    AtomicWriter& operator<<( std::ostream&(*f)(std::ostream&) ) {
	st << f;
	return *this;
    }
    ~AtomicWriter() { stream << st.str(); }
};