Untitled

int i = 0;
while (i < (list.length - 2)) {
    open(input+list[i]);
    open(input+list[i+1]);
    open(input+list[i+2]);
    i=i+3;
    //3 files are open. Do any action you need to below)
    //action here
}

//resolve the last 1-2 files if any
while(i < list.length) {
    open(input+list[i]);
    i++;
}