{
TASK:apple
LANG:Pascal
}
program apple;
type path=array[1..4900]of string;
type mas=array[0..70,0..70]of integer;
var p:path;
    a:mas;
    x,y,i,j,k,l,n,m:integer;

begin
readln(n,m);
for i:=1 to n do
begin
for j:=1 to m do
read(a[i,j]);
readln;
end;

for i:=1 to n do
for j:=1 to m do
x:=x+a[i,j];
x:=x+m+n;
y:=x div 2;
writeln(y);


end.
