var sol,valo:array[-1..10000000]of int64;
    s,i,ct:longint;
    fi,fo:text;
procedure afla(s:integer);
begin
     for i:=0 to 1000000 do
        begin
             ct:=5;
             while ct<=i do
                begin
                     sol[i]:=sol[i]+trunc(i/ct);
                     ct:=ct*5;
                end;
             if sol[i]<>sol[i-1] then valo[sol[i]]:=i;
        end;
end;
begin
     assign(fi,'fact.in'); reset(fi);
     assign(fo,'fact.out'); rewrite(fo);
     read(fi,s); sol[-1]:=-1;
     afla(s);
     if valo[s]=0 then writeln(fo,'-1') else
     writeln(fo,valo[s]);
     close(fi);
     close(fo);
end.