var
x,y,z,n,i,pola,br:longint;
s:string;


begin
readln( n );

for i:=1 to n do
begin
        readln( s );
        if s='1/2' then inc(x);
        if s='1/4' then inc(y);
        if s='3/4' then inc(z);
end;

pola:=x div 2;
if (y > 2) and (x mod 2=1) then
begin
        inc(pola);
        y:=y-2;
end;

if z>y then
begin
        while y>0 do
        begin
                inc(br);
                dec(z);
                dec(y);
        end;
        br:=br+z;
end;
if z<y then
begin
        while z>0 do
        begin
                inc(br);
                dec(z);
                dec(y);
        end;

        if y mod 4= 0 then br:=br+y div 4 else br:=br+y div 4 +1;
end;

writeln(pola+br);

end.