#include <algorithm>
    #include <cctype>
    #include <string>
    #include <iostream>
    
    int main()
    {
       std::string test = "abc123";
       if ( std::none_of(test.begin(), test.end(), ::isdigit))
          std::cout << "All good\n"; 
       else
          std::cout << "You've entered an integer\n";
       test = "abcdef";
       if ( std::none_of(test.begin(), test.end(), ::isdigit))
          std::cout << "All good\n"; 
       else
          std::cout << "You've entered an integer\n";
    }