Const
        finp='branza.in';
        fout='branza.out';
Type
        mat=array [0..100000] of longint;
Var     q,c,p:mat;
        a:array [0..100000] of int64;
        t,n,s,f,r:longint;
        res:int64;
        fi,fo:text;

Procedure Doc;
        Var i:longint;
        Begin
                Assign(fi,finp);
                Reset(fi);
                Read(fi,n,s,t);
                For i:=1 to n do Read(fi,c[i],p[i]);
                Close(fi);
        end;

Procedure Push(i:longint);
        Begin
                While (f<=r) and (a[i]<=a[q[r]]) do dec(r);
                inc(r);
                q[r]:=i;
                If q[f]=i-t then inc(f);
        end;

Procedure Lam;
        Var i:longint;
        Begin
                f:=1;
                r:=0;
                For i:=1 to n do
                   Begin
                        a[i]:=int64(c[i])-int64(i*s);
                        Push(i);
                        res:=res+int64((int64(a[q[f]])+int64(i*s))*int64(p[i]));
                   end;
        end;

Procedure Inkq;
        Begin
                Assign(fo,fout);
                Rewrite(fo);
                Write(fo,res);
                Close(fo);
        end;

        Begin
                Doc;
                Lam;
                Inkq;
        end.