var f,g:text;a:array [1..10,1..10] of 0..2;i,j,m,n,k,d:integer;
procedure xl(x,y:integer);
var i,j,t,r:integer;
begin
if x>3 then t:=x-2 else t:=1;
if y>3 then r:=y-2 else r:=1;
for i:=t to x+2 do
for j:=r to y+2 do a[i,j]:=2;
end;
Begin
assign(f,'farm.inp');reset(f);
assign(g,'farm.out');rewrite(g);
readln(f,m,n);
readln(f,k);
for i:=1 to k do
begin
readln(f,j,k);
a[j,k]:=1;
end;
for i:=1 to m do
for j:=1 to n do
if a[i,j]=1 then xl(i,j);
for i:=1 to m do
for j:=1 to n do
if a[i,j]=0 then inc(d);
writeln(g,d);
close(g);
End.
