foo.cc: In function ‘int main()’:
foo.cc:7:16: warning: unused variable ‘len’ [-Wunused-variable]
    7 |         ll k,n,len=0,ans=0,cnt[16]={1,0,0,0,1,0,1,0,2,1,1,2,0,1,0,0};
      |                ^~~