microseconds for random number

#include <ctime>
#include <chrono>
#include <iostream>
#include <sstream>

#define SSTR( x ) static_cast< std::ostringstream & >( \
( std::ostringstream() << std::dec << x ) ).str()

int main()
{
    volatile int i = 0;
    auto start = std::chrono::steady_clock::now();
    while (i < 10000000) {
        ++i;
    }
    auto end = std::chrono::steady_clock::now();
    auto elapsed = std::chrono::duration_cast<std::chrono::microseconds>(end - start);

std::cout << std::endl << std::endl;
int nn;
nn=elapsed.count();
std::string s = SSTR( nn );

std::cout << " Two random digits : " << s << std::endl;
}