program fact;
 var n,y,z,f:int64;
begin
 assign(input,'fact.in'); reset(input);
 assign(output,'fact.out'); rewrite(output);
 readln(y);
 if y=0 then write(1)
        else begin
             n:=4*y; 
             n:=n-n mod 5;
	     f:=5; 
             while (f<=n) do begin 
			     z:=z+n div f;
		             f:=f*5;
			     end;
 	     repeat
 	           if z<y then n:=n+5;
                   f:=n; 
                   while f mod 5=0 do begin 
			              inc(z); 
                                      f:=f div 5; 
                                      end;
             until z>=y;
             if z=y then write(n)
                    else write(-1);
             end;
 close(input); close(output);
end.