#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

char*mmap();
#define RD(v) int v=0;{int c;while(c=*rp++-48,c>=0)v=v*10+c;}
#define RDL(v) long v=0;{int c;while(c=*rp++-48,c>=0)v=v*10+c;}

long x[100002],a[100002];

main(){
	char*rp=mmap(0l,20l*200002,1,2,0,0ll);
	RD(n); RD(k);
	for(int i=0;++i<=n;){
		int neg=*rp==45?++rp,1:0;
		RDL(t);
		x[i]=neg?-t:t;
	}
	x[0]=1l<<63;
	x[n+1]=x[0]-1;
	for(int i=0;++i<=n;){
		RDL(t);
		a[i]=t;
	}
	int ai=k,bi=k;
	long ax=x[k]-a[k],bx=x[k]+a[k];
	long prev_ax;
	do{
		prev_ax=ax;
		while(x[ai-1]>=ax){
			--ai;
			if(ax>x[ai]-a[ai]) ax=x[ai]-a[ai];
			if(bx<x[ai]+a[ai]) bx=x[ai]+a[ai];
		}
		while(x[bi+1]<=bx){
			++bi;
			if(ax>x[bi]-a[bi]) ax=x[bi]-a[bi];
			if(bx<x[bi]+a[bi]) bx=x[bi]+a[bi];
		}
	}while(prev_ax!=ax);

	printf("%d",bi-ai+1);
}