convert custom hex code to string in c++

I'm trying to write simple encryption, please take look at below code I expecting it return

hello

by map with mapOfWords array

How to write decode function so, it return string as I'm expecting

#include <iostream>
#include <string>
#include <map>

using namespace std;

std::string decode(const std::string& input) {
    std::map<std::string, std::string> mapOfWords;
    mapOfWords["d2"] = "h";
    mapOfWords["a3"] = "e";
    mapOfWords["c2"] = "l";
    mapOfWords["72"] = "l";
    mapOfWords["84"] = "o";

    std::string result = input;
    return result;
}

int main(int argc, char** argv) {
    std::string sot = decode("\xd2\xa3\xc2\x72\x84");
    std::cout << sot << std::endl;

    return 0;
}