set_block
set_block(&diff_a_head, x, ch | BLOCK_MASK);
set_block(&diff_a_head, x, ch | BLOCK_MASK);
set_block(&diff_a_head, x + 1, chn | BLOCK_MASK);
set_block(&diff_a_head, x, ch | BLOCK_MASK);
set_block(&diff_a_head, x, ch | BLOCK_MASK);
set_block(&diff_a_head, x + 1, chn | BLOCK_MASK);
set_block(&diff_a_head, x, ch | BLOCK_MASK);
set_block(&diff_a_head, x + 1, chn | BLOCK_MASK);
set_block(&diff_a_head, x, ch | BLOCK_MASK);
set_block(&diff_a_head, x, ch | BLOCK_MASK);
set_block(&diff_a_head, x, ch | BLOCK_MASK);
set_block(&diff_a_head, x, ch | BLOCK_MASK);
set_block(&diff_a_head, x, ch | BLOCK_MASK);
set_block(&diff_a_head, x, ch | BLOCK_MASK);
set_block(&diff_a_head, x, ch | BLOCK_MASK);