백준 1914 c++

#include <iostream>
#include <cmath>
#include <string>

using namespace std;

int input(int lower, int upper)
{
	//cout << "input()" << endl;
	int A;

	while (1)
	{
		cin >> A;
		if (A >= lower && A <= upper)
		{
			break;
		}
		else
		{
			;
		}
	}

	return A;
}

void hanoi(int n, int from, int to, int by)
{
	if (n == 1)
	{
		cout << from << " " << to << "\n";
	}
	else if(n <= 20)
	{
		hanoi(n - 1, from, by, to);
		cout << from << " " << to << "\n";
		hanoi(n - 1, by, to, from);
	}
}

int main(void)
{
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);

	int N, point;
	string total;

	N = input(1, 100);
	total = to_string(pow(2, N));
	point = total.find('.');//'.'의 위치 인덱스
	total = total.substr(0, point);//시작부터 '.'앞까지
	total[total.length() - 1] -= 1; //total 마지막 위치 값을 -1
	cout << total << "\n";
	if (N <= 20)
	{
		hanoi(N, 1, 3, 2);
	}
	else
	{
		;
	}

	return 0;
}