View Compilation Error

0_0_26147857_10500.cpp: In function 'void dfs(int, int, int)':
0_0_26147857_10500.cpp:23:22: error: 'lcm' was not declared in this scope
  if(lcm(tmp,vec[step])<=r) dfs(step+1,-flag,lcm(tmp,vec[step]));
                      ^