#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
 
 
std::string common_vowels(std::vector<std::string> const& words) {
   std::string vowels = "aeiou";
   std::string::iterator last = std::end(vowels);
 
   for (auto word : words) {
      std::sort(std::begin(word), std::end(word));
      last = std::set_intersection(
      	    std::begin(vowels), last
      	  , std::begin(word),   std::end(word)
      	  , std::begin(vowels));
   }
 
   return {std::begin(vowels), last};
}
 
 
int main() {
   std::vector<std::string> const words = {"waiidwad", "afaiiwd", "esfiad", "sefasefgi", "siegsa"};
 
   std::string const vowels = common_vowels(words);
 
   std::cout << vowels << std::endl;
}
 

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