View Compilation Error

220178_0_20368.cpp:2: error: variable or field `sum' declared void
220178_0_20368.cpp:2: error: `n' was not declared in this scope
220178_0_20368.cpp:3: error: expected `,' or `;' before '{' token
220178_0_20368.cpp: In function `int main()':
220178_0_20368.cpp:17: error: `sum' cannot be used as a function