bank.cpp: In function 'int f(int, int)':
bank.cpp:20:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i=0; i<a_bit[pos].size(); i++) {
                   ~^~~~~~~~~~~~~~~~~~
bank.cpp: In function 'int main()':
bank.cpp:27:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d",&n,&m);
     ~~~~~^~~~~~~~~~~~~~~
bank.cpp:29:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d",&a[i]);
         ~~~~~^~~~~~~~~~~~
bank.cpp:32:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d",&b[i]);
         ~~~~~^~~~~~~~~~~~