#include <iostream>
#include <iterator>
#include <string>
#include <regex>
 
int main() {
    std::string s = "1Hi15This10";
 
    std::regex number("(\\d+)");
    auto begin = std::sregex_iterator(s.begin(), s.end(), number);

    for (auto i = begin; i != std::sregex_iterator(); ++i) {
        std::cout << "  " << i->str() << '\n';
    }
}