Can somebody help me understand why testing() prints the same value (13) for x and y?

#include <vector>
#include <unordered_set>

void testing(int x, int y) {
   std::cout << x << " " << y << std::endl; 
}

int main() {
   std::unordered_set<int> tmp = {0, 1, 2, 3, 4};
   std::vector<int> tmp1 = {10, 11, 12, 13, 14};
   auto itr = tmp.begin();
   testing(tmp1[*itr], tmp1[*(++itr)]);
   return 0;
}

This works fine:

testing(tmp1[*itr], tmp1[*std::next(itr)])

I get 14 and 13. I don’t understand why the same argument is passed to testing() in the first case.