// lazy = 2
// 0 0(originalStartIndex)        2(originalStartIndex + lazy)
// 1 0(originalStartIndex - lazy) 3(originalStartIndex + lazy)
// 2 0(originalStartIndex - lazy) 4(originalStartIndex + lazy)
// 3 1(originalStartIndex - lazy) 4(originalStartIndex + lazy - 1)
// 4 2(originalStartIndex - lazy) 4(originalStartIndex)
clean up