View Compilation Error

0_0_16222174_3173.cpp: In function 'void DP()':
0_0_16222174_3173.cpp:11:21: error: 'sum' was not declared in this scope
         for(int j = sum*2;j>=a[i];j--) {
                     ^
0_0_16222174_3173.cpp: In function 'int main()':
0_0_16222174_3173.cpp:21:51: error: 'sum' was not declared in this scope
     for(int i = 1;i <= n; i++) scanf("%d", &a[i]),sum+=a[i];
                                                   ^