Swap \(S_{2i-1}\) and \(S_{2i}\) actually for each \(i = 1,2, \ldots, \frac{|S|}{2}\) and print the resulting \(S\). Depending on the language you use, the index may differ by one from the problem statement, because many languages adopt \(0\)-based indexing.

Sample code

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

int main() {
	string s;
	cin >> s;
	int n = s.size(); // s の長さを取得
	for (int i = 0; i < n / 2; i++) swap(s[2 * i], s[2 * i + 1]);
	cout << s << '\n';
}