View Compilation Error

0_0_29290045_11445.cpp: In function 'int main()':
0_0_29290045_11445.cpp:44:26: error: 'a' was not declared in this scope
             scanf("%d", &a[i]);
                          ^
0_0_29290045_11445.cpp:45:26: error: 'sum' was not declared in this scope
             for (int j = sum; j >= 0; j--) {
                          ^
0_0_29290045_11445.cpp:51:13: error: 'sum' was not declared in this scope
             sum += a[i]; //dp记录的是最后的总容斥式的每一项系数.
             ^
0_0_29290045_11445.cpp:54:30: error: 'sum' was not declared in this scope
         for (int k = 0; k <= sum; k++)
                              ^
0_0_29290045_11445.cpp:57:31: error: 'a' was not declared in this scope
             ans = (ans * fact[a[i]]) % mod;
                               ^