View Compilation Error

0_0_31073697_5434.cpp: In function 'int main()':
0_0_31073697_5434.cpp:16:21: error: 'sum' was not declared in this scope
                     sum=sum+b;
                     ^
0_0_31073697_5434.cpp:18:23: error: 'sum' was not declared in this scope
                 cout<<sum<<endl;
                       ^