answer.code: In function ‘void dfs2(int, int)’:
answer.code:53:29: warning: iteration 17 invokes undefined behavior [-Waggressive-loop-optimizations]
   53 |     rep(i, 1, 18) par[u][i] = par[par[u][i - 1]][i - 1];
      |                   ~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
answer.code:14:39: note: within this loop
   14 | #define rep(i, a, b) for(int i = a; i <= b; i ++ )
      |                                       ^
answer.code:53:5: note: in expansion of macro ‘rep’
   53 |     rep(i, 1, 18) par[u][i] = par[par[u][i - 1]][i - 1];
      |     ^~~
/tmp/ccVpSURp.o: in function `__tcf_1':
answer.code:(.text+0x8): relocation truncated to fit: R_X86_64_PC32 against symbol `p' defined in .bss section in /tmp/ccVpSURp.o
/tmp/ccVpSURp.o: in function `__tcf_0':
answer.code:(.text+0x58): relocation truncated to fit: R_X86_64_PC32 against symbol `ve' defined in .bss section in /tmp/ccVpSURp.o
/tmp/ccVpSURp.o: in function `dfs(int, int)':
answer.code:(.text+0xa9): relocation truncated to fit: R_X86_64_PC32 against symbol `p' defined in .bss section in /tmp/ccVpSURp.o
answer.code:(.text+0xb2): relocation truncated to fit: R_X86_64_PC32 against symbol `dfn' defined in .bss section in /tmp/ccVpSURp.o
answer.code:(.text+0xbf): relocation truncated to fit: R_X86_64_PC32 against symbol `ve' defined in .bss section in /tmp/ccVpSURp.o
answer.code:(.text+0xc9): relocation truncated to fit: R_X86_64_PC32 against symbol `dfs_idx' defined in .bss section in /tmp/ccVpSURp.o
answer.code:(.text+0xe1): relocation truncated to fit: R_X86_64_PC32 against symbol `dfs_idx' defined in .bss section in /tmp/ccVpSURp.o
answer.code:(.text+0x159): relocation truncated to fit: R_X86_64_PC32 against symbol `p' defined in .bss section in /tmp/ccVpSURp.o
answer.code:(.text+0x1a7): relocation truncated to fit: R_X86_64_PC32 against symbol `bian' defined in .bss section in /tmp/ccVpSURp.o
answer.code:(.text+0x1ae): relocation truncated to fit: R_X86_64_PC32 against symbol `bian' defined in .bss section in /tmp/ccVpSURp.o
answer.code:(.text+0x1c9): additional relocation overflows omitted from the output
collect2: error: ld returned 1 exit status