code: function getConverters(from, to) {
          if (from === to) {
              return [];
          }
  
          if (CONVERTERS[from][to]) {
              return [to];
          }
  
          var queue = [from];
          var path = {};
          path[from] = [];
  
          while (queue.length) {
              var v = queue.shift();
              for (var w in CONVERTERS[v]) {
                  if (!path[w]) {
                      queue.push(w);
                      path[w] = path[v].concat([w]);
                      if (w === to) {
                          return path[w];
                      }
                  }
              }
          }
  
          return null;
      }
docs: Breadth-first search to find the conversion path