add index for isuwitter
add index for isuwitter

nin-gen-sei/yisucon,nin-gen-sei/yisucon,nin-gen-sei/yisucon,nin-gen-sei/yisucon,nin-gen-sei/yisucon,nin-gen-sei/yisucon,nin-gen-sei/yisucon,nin-gen-sei/yisucon,nin-gen-sei/yisucon