Update Failed after pushing

[spandan chakraborty]

I have an document like this

var versionSchema = new Schema({                    

            "versionId" : Number,

            "Actual_Start_Time" : Date,

            "Flag" : String,

            "country" : String,

            "state" : String,

});

I have pushed a two set of records into this schema * it generates _id in the schema also. Now can any one help me with the code for how can I update the value of Flag for the first record to Y which is set to N?

Please help, its Urgent for me