program stergeri;
var f,g:text;
    n,m,k,a,b,p,c2,l1,l2:int64;
    i:longint;
begin
assign(f,'stergeri.in');
assign(g,'stergeri.out');
reset(f);
rewrite(g);
read(f,n,m,k);
p:=k;
for i:=1 to m do
  begin
    read(f,a,b);
    if (a>k)then
    begin
      c2:=b-a+1;
      l1:=a;
      l2:=b;
    end else
    begin
      p:=p+b-a+1;
      if (p>=l1)and(c2>0)then
        begin
          inc(p,c2);
          c2:=0;
        end else
      if (c2>0)then
        begin
          dec(l1,b-a+1);
          dec(l2,b-a+1);
        end;
    end;
  end;
write(g,p);
close(f);
close(g);
end.