foo.cpp: In function 'int main()':
foo.cpp:10:24: error: 'memset' was not declared in this scope
  memset(a, 0, sizeof(a));
                        ^
foo.cpp:13:20: warning: unused variable 'C' [-Wunused-variable]
  int A = 0, B = 0, C = 0;
                    ^