50 ml of unknown concentration of hno2 is titrated with 25.7 ml of 0.0523 M KOH. What is the unknown concentration of the original HNO2 solution?

50 ml of unknown concentration of hno2 is titrated with 25.7 ml of 0.0523 M KOH.  What is the unknown concentration of the original HNO2 solution?  I got 0.0269 M for my answer and that was incorrect. Could you help me with this problem?

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