Hey, i really need some help.

i have an array with  numbers of frames.

like:
100
101
102
103
104
105
120
121
140
141
142
143

I dont need a single frames, I just want wo work with frames which are in a "group of frames". With for example 5 Frames.

i need this:
100
101
102
103
104
105
but not this:
120
121
and not this:
140
141
142
143


In the moment I check the frames
 with

for(int i=1; i<datei.length; i++) {
  if(element[i-1].frame-element[i].frame>=-1) {
      println (element[i-1].frame);
      println (element[i].frame);
}
but how can i check if the frame is in a "group of frames" too?


thank you!





and sorry for my english.