#include <stdio.h>
#include <math.h>
#include <time.h>

int main()
{
    
	int n , i , j , prime_sum , sqrt_i , prime ;
	
	printf ( "Programmet beregner summen af primtallene fra 1 til n\n" ) ;
	printf ( "Angiv n: " ) ;
	scanf ( "%d" , &n ) ;
	
	prime_sum = 0 ;
	
	if ( n < 11 )
	{
		printf ( "Come on, you can do that!" ) ;
	}
	else
	{				
		i = 11 ;

		while ( i <= n )
		{
			sqrt_i = ( int ) ( floor ( sqrt ( i ) ) ) ;
			
			j = 3 ;
			
			while  ( j <= sqrt_i )
			{				
				if ( i % j == 0 )
				{					
					prime = 1 ;
					break ;
				}
				
				j = j + 2 ;
				
				prime = 0 ;
			}
			
			if ( prime == 0 )
			{
				prime_sum = prime_sum + i ;
			}
			
			i = i + 2 ;
		}
	
		prime_sum = prime_sum + 2 + 3 + 5 + 7 ;
	
		printf ( "%d\n" , prime_sum ) ;
	}
	
	return 0;
}