//uses math;
var n,m,i,num,ans:longint;
    ch:char;
    a,b:array[1..500000]of longint;
function max(a,b:longint):longint;
begin
 if a>b then exit(a)
 else exit(b); 
end;
begin
 readln(n,m);
 for i:=1 to m do begin
  read(ch); readln(num);
  case ch of
   '+':inc(a[num]);
   '-':inc(b[num]);
  end;
 end;
 ans:=0;
 for i:=1 to n do
 ans:=ans+max(a[i],b[i]);
 writeln(ans);
close(input);
close(output)
end.