#include <string>
#include <vector>

using namespace std;

string solution(string phone_number) {
    string answer = "";
    int size = phone_number.size();
    
    for(int i=0;i<size-4;i++){
        answer += "*";
    }
    for(int i=size-4;i<size;i++){
        answer+=phone_number[i];
    }
    return answer;
}