program stergeri;
var f,g:text;
    n,m,k,a,b,i,p,c2: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 c2:=b-a+1 else
    begin
      p:=p+c2+b-a+1;
      if (b<k)then c2:=0 else c2:=b-k+1;
    end;
  end;
write(g,p);
close(f);
close(g);
end.