#include <iostream>

using namespace std;

void SwapChars(char & c1, char& c2){
	char tmp = c1;
	c1 = c2;
	c2 = tmp;
}

void reverse(string S, int start_index, int end_index){
	if (start_index < end_index){
		SwapChars(S[start_index], S[end_index]);
		reverse(S, start_index+1, end_index-1);	
	}
}


int main(int argc, char** argv){
	if (argc!=2){
		cout << "Parameters: STRING_TO_BE_REVERSED\n";
		return 1;
	}
	string str = argv[1];
	reverse(str,0,str.size());
	cout << str << endl;
}