蒟蒻求助呜呜呜

#include <iostream>
#include <algorithm>
#include <cstring>
using namespace std;

const int N = 506;
char a[N];
char b[N];
int numsa[N];
int numsb[N];

int main() {
	cin >> a;
	cin >> b;
	int lena = strlen(a);
	int lenb = strlen(b);
	reverse(a, a + lena);
	reverse(b, b + lenb);
	for (int i = 0; i !='\0'; i++) {
		numsa[i] = a[i] - '0';
	}
	for (int i = 0; i !='\0'; i++) {
		numsb[i] = b[i] - '0';
	}

	//add
	for (int i = 0; i <= 500; i++) {
		numsa[i] += numsb[i];
		if (numsa[i] > 9) {
			numsa[i + 1] += numsa[i] / 10;
			numsa[i] = numsa[i] % 10;
		}
	}
	int flag = 0;
	for (int i = 500; i >= 0; --i) {
		if (numsa[i] != 0) {
			flag = 1;
		}
		if (flag == 1) {
			cout << numsa[i];
		}
	}
	if (flag == 0) {
		cout << 0 << endl;
	}
	return 0;
}