C++ :: Converting Multiple Lines Of Strings To Double

I am trying to convert multiple lines of strings to double with std::stod .... I used the code found on the website:

#include <iostream>
#include <sstream>
#include <string>
#include <fstream>
int main() {
std::string two_doubles =" 22145.365 -3564789";
std::string::size_type K;
double first = std::stod (two_doubles, &K);
double second = std::stod (two_doubles.substr(K));
}

The string starts with white spaces. I get this error message when compiling:

warning unused variable 'first'
warning unused variable 'second'

How do you convert the two numbers in the string two_doubles to doubles?