function solve(arr,n){
  var res = 0;
  const dogs = [];
  const cats = [];
  for (let i = 0; i<arr.length; i++){
    (arr[i] == 'D' ? dogs : cats).push(i)
  };

  dogs.forEach(dog => {
   for(let i = 0; i<cats.length; i++) {
     if (cats[i] >= dog-n && cats[i] <= dog+n){

       res = res + 1;
       cats.splice(i,1);

       break;
     };
   };
  });
   return res;



}