#include <iostream>
#include <iterator>
#include <algorithm>
#include <locale>
 
int main(int, char**)
{
	using iterator = std::istream_iterator<std::string>;
	auto const& end = iterator();
 
	for (auto it = iterator(std::cin); it != end; ++it) {
		auto const& token = *it;
		if (std::all_of(std::begin(token), std::end(token), [](auto&& c) { return std::isdigit(c, std::locale()); })) {
			std::cout << std::string(token.size(), 'x') << " ";
		} else {
			std::cout << token << " ";
		}
	}
 
    return 0;
}
 

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TXkgdXNlcklEIGlzIGpvaG4xNyBhbmQgbXkgNCBkaWdpdCBwaW4gaXMgMTIzNCB3aGljaCBpcyBzZWNyZXQu

My userID is john17 and my 4 digit pin is 1234 which is secret.