View Compilation Error

0_0_39560850_8116.cpp: In function 'long long int C(long long int, long long int)':
0_0_39560850_8116.cpp:27:48: error: 'mul' was not declared in this scope
   27 |         if( n>=0 && m>=0 && n>=m ) return c( c(mul[x] , ksm(mul[y],mod-2,mod)),ksm(mul[x-y],mod-2,mod));
      |                                                ^~~
0_0_39560850_8116.cpp: In function 'int main()':
0_0_39560850_8116.cpp:41:17: error: 'mul' was not declared in this scope
   41 |                 mul[0] = 1;
      |                 ^~~