本地CE，在线IDE是RE，交上去是WA和TLE，你让我怎么调！

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

std::string sliceString(const std::string& str, size_t start, size_t end) {
    size_t len = std::min(end, str.size()) - start;
    return str.substr(start, len);
}

int ax[9000001];
int main()
{
	for (int i=2; i<=9000000; i++)
		ax[i] = 1;
	for (int i=2; i<=9000000; i++)
	{
		if (ax[i] == 1)
		{
			for (int j=i*2; j<=9000000; j+=i)
				ax[j] = 0;	
		}	
	}
	int n;
	cin >> n;
	for (int i=(int)pow(10, n-1); i<(int)pow(10, n); i++)
	{
		string a1 = to_string(i);
		for (int j=0; j<a1.size(); j++)
		{
			int f=1;
			for (int k=0; k<=j; k++)
			{
				string a_1 = sliceString(a1, 1, k+2);
				int a2 = stoi(a_1);
				if (!(ax[a2]))  f = 0;
			}
			if (f == 1)
				cout << i << endl; 
		}
	}
	return 0;
}

大佬帮我看看，在线等！