To engage in a futile or impossible task, like counting grains of sand in the sea; to waste one's efforts on a labor in vain.
这项研究需要投入大量时间和精力，但如果方向错了，那便是入海算沙，毫无意义。
This research requires a lot of time and effort, but if the direction is wrong, it would be like counting grains of sand in the sea, utterly meaningless.
Era:
Ancient
Frequency:
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