[{"_id":1,"Region":"North America","TotalSales":200000,"Countries":[{"name":"USA","sales":150000},{"name":"Canada","sales":50000},{"name":"Mexico","sales":10000},{"name":"Greenland","sales":5000},{"name":"Cuba","sales":2000},{"name":"Bahamas","sales":1000},{"name":"Jamaica","sales":500},{"name":"Haiti","sales":200},{"name":"Dominican Republic","sales":100}]},{"_id":2,"Region":"Europe","TotalSales":300000,"Countries":[{"name":"Germany","sales":100000},{"name":"France","sales":80000},{"name":"UK","sales":50000},{"name":"Italy","sales":30000},{"name":"Spain","sales":20000},{"name":"Portugal","sales":10000}]},{"_id":3,"Region":"Asia","TotalSales":400000,"Countries":[{"name":"China","sales":200000},{"name":"India","sales":100000},{"name":"Japan","sales":50000},{"name":"South Korea","sales":40000},{"name":"Indonesia","sales":30000},{"name":"Philippines","sales":20000},{"name":"Vietnam","sales":10000},{"name":"Malaysia","sales":5000},{"name":"Singapore","sales":2000},{"name":"Thailand","sales":1000}]}]

db.collection.aggregate([{$unwind:"$Countries"},{$sort:{"Countries.sales":1}},{$group:{_id:"$_id",Countries:{$push:"$Countries"},Region:{"$first":"$Region"},TotalSales:{"$first":"$TotalSales"}}},{$project:{Region:1,TotalSales:1,Countries:{$slice:["$Countries",5]}}}])