View Compilation Error

0_0_21811862_27137.cpp: In function 'int main()':
0_0_21811862_27137.cpp:59:34: error: 'f' was not declared in this scope
   for(int i = 1; i < maxn; ++i)  f[i] = (f[i-1]<<1LL) % mod;
                                  ^
0_0_21811862_27137.cpp:65:5: error: expected primary-expression before '}' token
     }
     ^