#include <stdio.h>
#include <stdlib.h>

#define MAX_N 101000

int isPrime[ MAX_N + 1 ] = { 0, 0, 1 };

int compare( const void *, const void * );

int main( void ) {
	int i, j, N, P, cnt, p[ 22 ], sum[ 253 ];

	for ( i = 3; i <= MAX_N; i += 2 )
		isPrime[ i ] = 1;

	for ( i = 3; i * i <= MAX_N; i += 2 )
		if ( isPrime[ i ] )
			for ( j = i * 2; j <= MAX_N; j += i )
				isPrime[ j ] = 0;

	for ( ; scanf( "%d %d", &N, &P ), N != -1; printf( "%d\n", sum[ P - 1 ] ) ) {
		cnt = 0;
		for ( i = N + 1; cnt < 22; i++ )
			if ( isPrime[ i ] )
				p[ cnt++ ] = i;

		cnt = 0;
		for ( i = 0; i < 22; i++ )
			for ( j = i; j < 22; j++ )
				sum[ cnt++ ] = p[ i ] + p[ j ];

		qsort( sum, 253, sizeof(int), &compare );
	}

	return 0;
}

int compare( const void *a, const void *b ) {
	return *(int *)a - *(int *)b;
}