input form set focus on iPad

[ai]

<label>IP Setting
    <input id="ip1" type="number" value="192" min="1" max="999"/>
    <input id="ip2" type="number" value="168" min="1" max="999"/>
    <input id="ip3" type="number" value="0" min="1" max="999"/>
    <input id="ip4" type="number" value="0" min="1" max="999"/>
</label>

the code is used for set IP address,  when touch any one of  these input forms ,the focus can only be set on the first one ,
 then the ipad virtual keyboard show up ,  how to adjust this to set focus on the touch one ?