Alien Invasion II

#include<iostream>
#include<math.h>
#include<string>

using namespace std;

/*bool Prime(long long n)
{
	bool prime = 1;

	for (int i = 2; i * i <= n && (n % i || (prime = 0)); i++);

	return prime;
}
*/

bool Prime(long long n)
{
	int cnt = 0;
	long long  i;

	for (i = 2; i <= sqrt(n) && cnt<1; i++)
	{
		if (n % i == 0)
		{
			cnt++;
		}
	}
	
	if (cnt < 1)
		return true;

	return false;
}
/*
void Factors(long long n)
{
	int cnt = 0;
	long long  i;

	for (i = 2; i <= sqrt(n) && cnt<1; i++)
	{
		if (n % i == 0)
		{
			cout << i << " ";
			cnt++;
		}
	}
	cout << (n/(i-1))<<endl;
}*/
int main()
{
	long long n,n1;
	string s,s1;
	bool b=1;

	cin >> n;
	n1 = n;

		
	long long i = 1;

	b = Prime(n1);

		while (b == 1)
		{
			s = to_string(n);
			s1 = to_string(i);

			s = s1 + s;
		
			n1 = stoi(s);

			b = Prime(n1);
			
			i++;
		}

		cout << n1 << endl;
		//Factors(n1);

}

Test 1

Verdict: RUNTIME ERROR

terminate called after throwing an instance of 'std::out_of_range'
  what():  stoi

Test 2

Verdict: WRONG ANSWER

Test 3

Verdict: WRONG ANSWER