foo.cc: In function ‘int main()’:
foo.cc:25:5: error: ‘vector’ was not declared in this scope
   25 |     vector<int> a, b;
      |     ^~~~~~
foo.cc:4:1: note: ‘std::vector’ is defined in header ‘<vector>’; this is probably fixable by adding ‘#include <vector>’
    3 | #include <string>
  +++ |+#include <vector>
    4 | using namespace std;
foo.cc:25:12: error: expected primary-expression before ‘int’
   25 |     vector<int> a, b;
      |            ^~~
foo.cc:31:13: warning: comparison of integer expressions of different signedness: ‘int’ and ‘const std::__cxx11::basic_string<char>::size_type’ {aka ‘const long unsigned int’} [-Wsign-compare]
   31 |     if (pos != string::npos) da = (int)A.size() - pos - 1;
      |         ~~~~^~~~~~~~~~~~~~~
foo.cc:34:13: error: ‘a’ was not declared in this scope
   34 |             a.push_back(cv(c));
      |             ^
foo.cc:38:13: warning: comparison of integer expressions of different signedness: ‘int’ and ‘const std::__cxx11::basic_string<char>::size_type’ {aka ‘const long unsigned int’} [-Wsign-compare]
   38 |     if (pos != string::npos) db = (int)B.size() - pos - 1;
      |         ~~~~^~~~~~~~~~~~~~~
foo.cc:41:13: error: ‘b’ was not declared in this scope
   41 |             b.push_back(cv(c));
      |             ^
foo.cc:44:13: error: ‘a’ was not declared in this scope
   44 |     reverse(a.begin(), a.end());
      |             ^
foo.cc:45:13: error: ‘b’ was not declared in this scope
   45 |     reverse(b.begin(), b.end());
      |             ^
foo.cc:50:12: error: expected primary-expression before ‘long’
   50 |     vector<long long> c(na + nb + 1, 0);
      |            ^~~~
foo.cc:54:29: error: ‘nb’ was not declared in this scope; did you mean ‘na’?
   54 |         for (int j = 0; j < nb; j++)
      |                             ^~
      |                             na
foo.cc:55:13: error: ‘c’ was not declared in this scope
   55 |             c[i + j] += 1LL * a[i] * b[j];
      |             ^
foo.cc:58:34: error: ‘c’ was not declared in this scope
   58 |     for (int i = 0; i + 1 < (int)c.size(); i++){
      |                                  ^
foo.cc:64:19: error: ‘c’ was not declared in this scope; did you mean ‘dc’?
   64 |     int sz = (int)c.size();
      |                   ^
      |                   dc