7問目。

By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13.

What is the 10001st prime number?

#include <iostream>

using namespace std;


long long  int primeCall(unsigned int NM){

	long long int prime[50000];
	long long int *box=new long long int[1000000];

	long long int p=0;

	for(p=0;p<NM;p++)prime[p]=0;
	prime[0]=2;
	box[0]=0;

	for(p=1;p<=NM;p++)
	{	
		for(long long int i=prime[p-1];i<1000000;i++)
		{
			if((i%prime[p-1])==0)box[i]=0;
			else if (box[i]!=0)box[i]=i;			
		}
		
		for(long long int i=2;i<1000000;i++)
		{
			if(box[i]!=0)
			{
				prime[p]=i;
				break;
			}
		}
	}

	delete [] box;

	return prime[NM-1];
}
int main()
{
	cout<<primeCall(10001)<<endl;
}