div4
out[i] = div4(3*in_near[i] + in_far[i] + 2);
out[1] = div4(input[0]*3 + input[1] + 2);
out[i*2+0] = div4(n+input[i-1]);
out[i*2+1] = div4(n+input[i+1]);
out[i*2+0] = div4(input[w-2]*3 + input[w-1] + 2);
out[0] = out[1] = div4(3*in_near[0] + in_far[0] + 2);
out[0] = div4(t1+2);
out[w*2-1] = div4(t1+2);