/in/foo.cc: In function 'int main()':
/in/foo.cc:14:28: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%lld%lld",&n,&m);
                            ^
/in/foo.cc:15:62: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     for(long long int i = 1;i <= n;i ++)  scanf("%lld",&a[i]);
                                                              ^