View Compilation Error

0_0_13920980_32019.cpp: In function 'void solve()':
0_0_13920980_32019.cpp:78:25: error: 'len' cannot be used as a function
                 if (len()>1)
                         ^
0_0_13920980_32019.cpp:80:40: error: 'len' cannot be used as a function
                     for (int k=1;k<len();k++)
                                        ^
0_0_13920980_32019.cpp:81:44: error: 'len' cannot be used as a function
                         for (int l=1;l<len();l++)
                                            ^
0_0_13920980_32019.cpp:83:40: error: 'len' cannot be used as a function
                     for (int k=0;k<len();k++)
                                        ^
0_0_13920980_32019.cpp:84:46: error: 'len' cannot be used as a function
                         for (int l=k+1;l<len();l++)
                                              ^
0_0_13920980_32019.cpp:91:41: error: 'len' cannot be used as a function
                     ans=(LL)ans*det(len())%MOD;
                                         ^