View Compilation Error

0_0_29063816_11506.cpp: In function 'void dfs(int, int)':
0_0_29063816_11506.cpp:2:2: error: 'sum' was not declared in this scope
  sum+=gcd(gc,a[i]);
  ^
0_0_29063816_11506.cpp:2:14: error: 'a' was not declared in this scope
  sum+=gcd(gc,a[i]);
              ^
0_0_29063816_11506.cpp:2:18: error: 'gcd' was not declared in this scope
  sum+=gcd(gc,a[i]);
                  ^
0_0_29063816_11506.cpp:5:11: error: 'n' was not declared in this scope
  for(i; i<n; i++) {
           ^
0_0_29063816_11506.cpp:8:16: error: 'C' was not declared in this scope
    sum+=C(i,n-i);
                ^