#include <bits/stdc++.h>
using namespace std;

int main() {
	long long int num,i=0;
	string ans = "";
	char str[16] = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
	scanf("%lld",&num);
	if(num==0) {
		cout<< 0 ;
	} else {
		while(num) {
			ans+=str[num % 16];//n
			num /= 16;
		}
		for (int i = ans.size() - 1; i >= 0; i--) {
			cout << ans[i];
		}
	}
}

跟 年号字串差不多。