import java.util.*; import java.io.*; public class Main { public static void main(String[] args){ FastScanner scanner = new FastScanner(); int n = scanner.nextInt(); int k = scanner.nextInt()-1; long[] x = new long[n]; long[] a = new long[n]; for(int i = 0; i < n; i++){ x[i] = scanner.nextLong(); } for(int i = 0; i < n; i++){ a[i] = scanner.nextLong(); } long min = x[k]-a[k]; long max = x[k]+a[k]; for(int i = k; i >= 0; i--){ if(x[i] >= min){ min = Math.min(min,x[i]-a[i]); max = Math.max(max,x[i]+a[i]); } } for(int i = k; i < n; i++){ if(x[i] <= max){ min = Math.min(min,x[i]-a[i]); max = Math.max(max,x[i]+a[i]); } } int start = -1; int end = n; for(int i = 0; i < n; i++){ if(x[i] >= min){ start = i; break; } } for(int i = n-1; i >= 0; i--){ if(x[i] <= max){ end = i; break; } } if(start == end){ if(n == 1){ System.out.println(1); return; }else{ if(start >= 0 && end < n){ System.out.println(1); }else{ System.out.println(0); } } }else if(start != end){ System.out.println(end-start+1); } } public static int upperBound(long[] array, long value) { int low = 0; int high = array.length; int mid; while( low < high ) { mid = ((high - low) >>> 1) + low; // (high + low) / 2 if( array[mid] <= value ) { low = mid + 1; } else { high = mid; } } return low; } public static final int lowerBound(final long[] arr, final long value) { int low = 0; int high = arr.length; int mid; while (low < high){ mid = ((high - low) >>> 1) + low; //(low + high) / 2 (オーバーフロー対策) if (arr[mid] < value) { low = mid + 1; } else { high = mid; } } return low; } private static class FastScanner { private final InputStream in = System.in; private final byte[] buffer = new byte[1024]; private int ptr = 0; private int buflen = 0; private boolean hasNextByte() { if (ptr < buflen) { return true; }else{ ptr = 0; try { buflen = in.read(buffer); } catch (IOException e) { e.printStackTrace(); } if (buflen <= 0) { return false; } } return true; } private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;} private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;} public boolean hasNext() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++; return hasNextByte();} public String next() { if (!hasNext()) throw new NoSuchElementException(); StringBuilder sb = new StringBuilder(); int b = readByte(); while(isPrintableChar(b)) { sb.appendCodePoint(b); b = readByte(); } return sb.toString(); } public long nextLong() { if (!hasNext()) throw new NoSuchElementException(); long n = 0; boolean minus = false; int b = readByte(); if (b == '-') { minus = true; b = readByte(); } if (b < '0' || '9' < b) { throw new NumberFormatException(); } while(true){ if ('0' <= b && b <= '9') { n *= 10; n += b - '0'; }else if(b == -1 || !isPrintableChar(b)){ return minus ? -n : n; }else{ throw new NumberFormatException(); } b = readByte(); } } public int nextInt() { long nl = nextLong(); if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) throw new NumberFormatException(); return (int) nl; } public double nextDouble() { return Double.parseDouble(next());} } }