I need a tip to solve this problem

/*Write either a C++ function int triplets(stack<string> words) or a Java method public static
 * int triplets(Stack<String> words) that take as the argument a stack of strings and count how
 * many elements are included in the stack exactly three times. You should use objects of type
 * set<string> in C++ or TreeSet<String> in Java. The set operations are given below (refer to
 * Problem 1 for the stack operations):
*/


#include <iostream>
#include <stack>
#include <set>
#include <string>
using namespace std;

string popped="";
int triplets(stack<string>words)
{
    set<string>set1{"wow", "AUA", "wow", "AUA", "Data  Structures", "AUA", "OOP", "wow"} ;
    for(const auto &count: set1)
    {
        words.push(count);

    }
    for(int i=0; i<words.size(); i++)
    {

        for(int current=i; current<words.size(); current++)
        {
            popped=words.top();

        }
    }

}