var a,b:array[0..100000] of longint; f1,f2:text; i,x,n,l,max,nr:longint;

procedure pozitie(var m:longint; p,u:longint);
var i,j,di,dj,aux:longint;
begin
di:=0;
dj:=-1;
i:=p;
j:=u;
while i<j do
begin
if a[i]>a[j] then
begin
aux:=di;
di:=-dj;
dj:=-aux;
aux:=a[i];
a[i]:=a[j];
a[j]:=aux;
aux:=b[i];
b[i]:=b[j];
b[j]:=aux;
end;
i:=i+di;
j:=j+dj;
end;
m:=i;
end;

procedure quick(p,u:longint);
var m:longint;
begin
if p<u then
begin
pozitie(m,p,u);
quick(p,m-1);
quick(m+1,u);
end;
end;

begin
        assign(f1,'lupu.in');
        reset(f1);
        assign(f2,'lupu.out');
        rewrite(f2);
        read(f1,n,x,l);
        for i:=1 to n do readln(f1,a[i],b[i]);
        quick(1,n);
        max:=-maxlongint;
        for i:=n downto 1 do begin
                if a[i]+l>x then if max<b[i] then max:=b[i];
                if a[i-1]+l<=x then
                        begin
                                inc(nr,max);
                                max:=-maxlongint;
                                x:=x-l;
                        end;
        end;
        if max<>-maxlongint then nr:=nr+max;
        writeln(f2,nr);
        close(f1);
        close(f2);
end.