foo.cc: In function 'int main()':
foo.cc:5:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d", &a, &b);
     ~~~~~^~~~~~~~~~~~~~~~
foo.cc:6:37: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     for(int i = 0; i < a; i++) scanf("%d", &x[i]);
                                ~~~~~^~~~~~~~~~~~~
foo.cc:7:37: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     for(int i = 0; i < b; i++) scanf("%d", &y[i]);
                                ~~~~~^~~~~~~~~~~~~