View Compilation Error

0_0_17085880_11495.cpp: In function 'int main()':
0_0_17085880_11495.cpp:14:35: error: 'a' was not declared in this scope
                 for(int j=2000;j>=a[i];j--)dp[j]=dp[j]|dp[j-r[i]];     
                                   ^