#include <iostream>
#include <string>
using namespace std;
string s = "";
string reverse(string str,int len) {
    if(len == 0) return "" + str[0];
    return str[len-1] + reverse(str,len-1);
}
int main(void) {
    string str = "helloworld";
    int len = str.size();   
    string s = reverse(str,len);
    cout << s;
}