foo.cc: In member function 'BigInteger BigInteger::operator+(const BigInteger&) const':
foo.cc:47:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if (g == 0 && i >= s.size() && i >= b.s.size()) break;
                  ~~^~~~~~~~~~~
foo.cc:47:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if (g == 0 && i >= s.size() && i >= b.s.size()) break;
                                   ~~^~~~~~~~~~~~~
foo.cc:49:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if (i < s.size()) x += s[i];
        ~~^~~~~~~~~~
foo.cc:50:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if (i < b.s.size()) x += b.s[i];
        ~~^~~~~~~~~~~~
foo.cc: In member function 'BigInteger BigInteger::operator-(const BigInteger&) const':
foo.cc:61:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if (g == 0 && i >= s.size() && i >= b.s.size()) break;
                  ~~^~~~~~~~~~~
foo.cc:61:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if (g == 0 && i >= s.size() && i >= b.s.size()) break;
                                   ~~^~~~~~~~~~~~~
foo.cc:63:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if (i < b.s.size()) x -= b.s[i];
        ~~^~~~~~~~~~~~
foo.cc: In member function 'BigInteger BigInteger::operator*(const BigInteger&) const':
foo.cc:78:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(i=0; i<s.size(); i++) for(j=0; j<b.s.size(); j++) v[i+j]+=LL(s[i])*b.s[j];
            ~^~~~~~~~~
foo.cc:78:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(i=0; i<s.size(); i++) for(j=0; j<b.s.size(); j++) v[i+j]+=LL(s[i])*b.s[j];
                                      ~^~~~~~~~~~~
foo.cc:80:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if (g ==0 && i >= v.size()) break;
                 ~~^~~~~~~~~~~
foo.cc: In function 'std::ostream& operator<<(std::ostream&, const BigInteger&)':
foo.cc:168:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int j = 0; j < strlen(buf); j++) out << buf[j];
                   ~~^~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:190:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d", &n, &m);
  ~~~~~^~~~~~~~~~~~~~~~
foo.cc:194:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d%d%d", &a, &b, &c, &d);
   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

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