View Compilation Error

0_0_22998042_28070.cpp: In function 'int main()':
0_0_22998042_28070.cpp:76:40: error: 'nt_permutation' was not declared in this scope
         }while(nt_permutation(a+2,a+n+1));//因为是个环，所以只需要全排列（n-1）个数就好，少了一个*n的复杂度
                                        ^