View Compilation Error

0_0_16222121_18370.cpp: In function 'int main()':
0_0_16222121_18370.cpp:12:27: error: 'memset' was not declared in this scope
   memset(dp, 0, sizeof(dp));
                           ^
0_0_16222121_18370.cpp:13:16: error: 'n' was not declared in this scope
   scanf("%d", &n);
                ^
0_0_16222121_18370.cpp:15:16: error: 'a' was not declared in this scope
    scanf("%d", a + i);
                ^
0_0_16222121_18370.cpp:17:20: error: 'a' was not declared in this scope
   dp[0][0] = dp[0][a[0]] = true;
                    ^