View Compilation Error

0_0_39459325_32525.cpp: In function 'int mg(int&, int&, int, int, ull, ull, ull, ull, ull&)':
0_0_39459325_32525.cpp:65:41: error: 'f' was not declared in this scope
   65 |                         s[nk] = s[k1] + f[k2];
      |                                         ^