求个大佬帮看看┭┮﹏┭┮

错得好像亿点多

#include <iostream>
using namespace std;
int p;
int len;
int a[1000005];

int main() {
	cin >> p;
	a[0] = 1;
	for (int i = 1; i <= p; i++) {
		for (int j = 0; j <= len; j++)
			a[j] *= 2;
		for (int j = 0; j <= len; j++) {
			if (a[j] >= 10) {
				a[j + 1] += a[j] / 10;
				a[j] %= 10;
			}
			if (a[len + 1])
				len++;
		}
	}
	a[0]--;
	cout << len + 1 << endl;
	for (int i = 499; i >= 0; i--)
		cout << a[i];
	return 0;
}