# [Stax](https://github.com/tomtheisen/stax), <s>12</s> <s>14</s> 13 [bytes](https://github.com/tomtheisen/stax/blob/master/docs/packed.md#packed-stax) àJ├∙ε╝F▀ÿi☻Ia [Run and debug it](https://staxlang.xyz/#p=854ac3f9eebc46df9869024961&i=[[11,+28],+[12,+16],+[4],+[]],+2%0A[[11,+28],+[12,+16],+[4],+[]],+5%0A[[7,+144],+[12],+[4,+8],+[3,+4,+6]],+1%0A[[7,+144],+[12],+[4,+8],+[3,+4,+6]],+10%0A[[30],+[40],+[50,+60],+[70,+80,+90]],+2%0A[[30],+[40],+[50,+60],+[80,+90]],+7%0A[[15],+[30],+[2,+3,+5],+[4,+5,+10]],+3%0A[[15],+[30],+[2,+3,+5],+[4,+5,+10]],+7&m=2) Explanation: vsc{%vfr$r+@]|u Full program, unpacked, implicit input vs Decrement the number and get the list c{ f Copy and filter: %v Length not equal to 1? r$r Reverse, flatten, and reverse again + Concat orig array and and modified array @]|u Index, wrap into array, uneval ## Stax, 12 bytes Å{b≈\☼╣Δ@░ ‼ Unpacked: {vsc{%vfr$r+@} This is a block, so I can get rid of the `]|u`, but I don't know if this is valid as it's packing a block.