Scanf.scanf "%d %d %d %d" (fun sx sy tx ty ->
    for i = sx to tx do print_char 'R' done;
    for i = sy to ty do print_char 'U' done;
    for i = sx to tx do print_char 'L' done;
    for i = sy to ty do print_char 'D' done;
    print_char 'D';
    for i = sx to tx + 1 do print_char 'R' done;
    print_char 'U';
    for i = sy to ty do print_char 'U' done;
    print_char 'L';
    print_char 'U';
    for i = sx to tx + 1 do print_char 'L' done;
    print_char 'D';
    for i = sy to ty do print_char 'D' done;
    print_char 'R';
    print_newline ()
)
