/in/foo.cc: In function 'int main()':
/in/foo.cc:10:24: error: 'memset' was not declared in this scope
  memset(a, 0, sizeof(a));
                        ^
/in/foo.cc:8:12: warning: unused variable 'ans' [-Wunused-variable]
  int flag, ans, ans1, ans2, sum1 = 0,sum2 = 0;
            ^~~