type arr=array[1..10000]of longint;
var n,m,i,j,ans,sum:longint;
a,b:arr;
procedure qs(var a:arr;l,r:longint);
var i,j,mid,t:longint;
begin
i:=l;j:=r;mid:=a[(l+r)shr 1];
repeat
while(a[i]<mid)do inc(i);
while(a[j]>mid)do dec(j);
if(i<=j)then
begin
t:=a[i];a[i]:=a[j];a[j]:=t;
inc(i);dec(j);
end;
until i>j;
if(j>l)then qs(a,l,j);
if(i<r)then qs(a,i,r);
end;
begin
readln(n,m);
for i:=1 to n do read(a[i]);
qs(a,1,n);
for i:=1 to m do read(b[i]);
qs(b,1,m);
j:=1;i:=1;
while(i<=n)and(j<=m)do
begin
if(b[j]>=a[i])and(sum<2)then
begin
inc(i);
inc(sum);
inc(ans);
end;
if(b[i]<a[i])or(sum=2)then
begin
inc(j);sum:=0;
end;
end;
writeln(ans);
end.