#include <cstdio>
#include <cmath>
#define rep( i, n, m ) for(ll i = ( n ); i < ( m ); i++)
using ll = long long int;

int give_water( int* array, int begin, int end );

int main( void ){
	int n, k;
	if (!scanf( "%d %d", &n, &k ))
		return 0;
	k--;
	ll* position = new ll( n * 2 );
	rep( i, 0, n ){
		if (!scanf( "%lld", position + i ))
			return 0;
	}
	rep( i, 0, n ){
		if (!scanf( "%lld", position + i + n ))
			return 0;
	}
	ll area[ 2 ];
	area[ 0 ] = position[ k ] - position[ n + k ];
	area[ 1 ] = position[ k ] + position[ n + k ];
	bool can = true;
	while(can){
		can = false;
		rep( i, 0, n ){
			if( area[ 0 ] <= position[ i ] && position[ i ] <= area[ 1 ]){
				if(area[ 0 ] > position[ i ] - position[ n + i ]){
					area[ 0 ] = position[ i ] - position[ n + i ];
					can = true;
				}
				if(area[ 1 ] < position[ i ] + position[ n + i ]){
					area[ 1 ] = position[ i ] + position[ n + i ];
					can = true;
				}
			}
		}
	}
	int sum = 0;
	rep( i, 0, n ){
		if(area[ 0 ] <= position[ i ] && position[ i ] <= area[ 1 ])
			sum++;
	}
	printf( "%d\n", sum );
	return 0;
}