View Compilation Error

0_0_25404703_25547.cpp: In function 'void solver(int, int)':
0_0_25404703_25547.cpp:102:18: error: return-statement with a value, in function returning 'void' [-fpermissive]
  if (l>r) return 1;
                  ^
0_0_25404703_25547.cpp:104:53: error: invalid use of void expression
  res=mul(res,mul(mul(solver(l,pos-1),solver(pos+1,r)),C(r-l,pos-l)));
                                                     ^
0_0_25404703_25547.cpp: In function 'int main()':
0_0_25404703_25547.cpp:130:29: error: invalid use of void expression
   res=mul(solver(1,n),inv[n]);
                             ^