#include <algorithm>
#include <iostream>

char caesar(char c)
{
  return c+3;
}

char subtract(char c, char ziffer)
{
  return c - (ziffer-'0');
}

int main()
{
  char s[] = "Hallo Welt";
  const char c[] = "123123123123";

  std::cout << s << '\n';
  std::transform(s, s+10, s, caesar);
  std::cout << s << '\n';
  std::transform(s, s+10, c, s, subtract);
  std::cout << s << '\n';
}