#include <iostream>
#include <vector>
#include <algorithm>
#include <unordered_map>
 
template <typename T> 
using CounterMap = std::unordered_map<T, std::size_t>;
 
int main() {
  std::vector<int> vec = {1, 2, 3, 3, 2, 1, 1, 2, 3, 3};
 
  CounterMap<int> counter;
 
  for (int value : vec) {
    ++counter[value];      
  }
 
  std::cout << max_element(counter.begin(),
                           counter.end(),
                           [](const CounterMap<int>::value_type &lhs,
                              const CounterMap<int>::value_type &rhs) {
                             return lhs.second < rhs.second; 
                           })->first;
  return 0;  
}

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