text: #define _GLIBCXX_DEBUG           1 // for debug mode
  #define _GLIBCXX_SANITIZE_VECTOR 1 // for asan on vectors
  #pragma GCC optimize("O3", "unroll-loops")
  #pragma GCC optimize("fast-math")
  #pragma GCC target("avx,avx2,abm,bmi,bmi2") // tip: `lscpu`
  // before a loop
  #pragma GCC unroll 16 // 0 or 1 -> no unrolling
  #pragma GCC ivdep
  