View Compilation Error

0_0_17902605_12239.cpp: In function 'int main()':
0_0_17902605_12239.cpp:10:3: error: 'sum' was not declared in this scope
   sum+=i;
   ^
0_0_17902605_12239.cpp:11:9: error: 'sum' was not declared in this scope
   cout<<sum<<endl;
         ^