#include <iostream>
#include <string>
using namespace std;
string SP(string s1, string s2) {
	int i = s1.size() - 1, j = s2.size() - 1;
	int k = 0;
	string res = "";
	while (i >= 0 && j >= 0) {
		res = char((s1[i] - '0' + s2[j] - '0' + k) % 10 + '0') + res;
		k = (s1[i] - '0' + s2[j] - '0' + k) / 10;
		i--, j--;
	}
	while (i >= 0) {
		res = char((s1[i] - '0' + k) % 10 + '0') + res;
		k = (s1[i] - '0' + k) / 10;
		i--;
	}
	while (j >= 0) {
		res = char((s2[j] - '0' + k) % 10 + '0') + res;
		k = (s2[j] - '0' + k) / 10;
		j--;
	}
	if (k)
		res = char(k + '0') + res;
	return res;
}

string SM(string s1, int a) {
	int k = 0;
	string res = "";
	for (int i = s1.size() - 1; i >= 0; i--) {
		res = char(((s1[i] - '0') * a + k) % 10 + '0') + res;
		k = ((s1[i] - '0') * a + k) / 10;
	}
	if (k)
		res = char(k + '0') + res;
	return res;
}
int main() {
	int n;
	cin >> n;
	string res = "0", temp = "1";
	for (int i ...