parenting.js

function processData(input) {
  var i = 1;
  var lines = input.split("\n");
  var t = parseInt(lines[0]);
  for (l=0; l<t; l++) {
     var n = parseInt(lines[i]);
     i++;
     var mat = lines.slice(i,i+n).map((m,v)=>[...m.split(" ").map(s=>parseInt(s)),v]);
     mat.sort(function(a,b) {return a[0]-b[0]})
     var possible = true;
     var ans = [];
     ans[mat[0][2]] = "J";
     var j,c;
     j = mat[0];
     c=[0,0];
     for (x=1; x<mat.length; x++) {
         if (mat[x][0]>=j[1]) {ans[mat[x][2]]="J";j=mat[x];}
         else if (mat[x][0]>=c[1]) {ans[mat[x][2]]="C";c=mat[x];}
         else {possible = false; break;}
     }
     console.log("Case #"+(l+1)+": "+(possible?ans.join(""):"IMPOSSIBLE")+"\n");
     i+=n;
  }
} 

process.stdin.resume();
process.stdin.setEncoding("ascii");
_input = "";
process.stdin.on("data", function (input) {
    _input += input;
});

process.stdin.on("end", function () {
   processData(_input);
});