看不懂题目，直接高精度

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
char A[8], B[8];
short a[7], b[7], c[7];
int main(){
	cin >> A >> B;
	a[0] = strlen(A) - 2, b[0] = strlen(B) - 2;
	for(int i = 1; i <= a[0]; i++){
		if(A[a[0] - i + 2] > '9') a[i] = A[a[0] - i + 2] - 'A' + 10;
		else a[i] = A[a[0] - i + 2] - '0';
	}
	for(int i = 1; i <= b[0]; i++){
		if(B[b[0] - i + 2] > '9') b[i] = B[b[0] - i + 2] - 'A' + 10;
		else b[i] = B[b[0] - i + 2] - '0';
	}
	c[0] = max(a[0], b[0]);
	for(int i = 1; i <= c[0]; i++){
		c[i] += a[i] + b[i];
		if(c[i] >= 16) c[i] -= 16, c[i + 1]++;
	}
	if(c[c[0] + 1]) c[0]++;
	cout << "0X";
	for(int i = c[0]; i >= 1; i--){
		if(c[i] >= 10) cout << char(c[i] - 10 + 'A');
		else cout << c[i];
	}

	return 0;
}