foo.cc: In member function 'BigInteger BigInteger::operator+(const BigInteger&) const':
foo.cc:39:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 if (g == 0 && i >= s.size() && i >= b.s.size()) break;
               ~~^~~~~~~~~~~
foo.cc:39:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 if (g == 0 && i >= s.size() && i >= b.s.size()) break;
                                ~~^~~~~~~~~~~~~
foo.cc:41:7: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 if (i < s.size()) x += s[i];
     ~~^~~~~~~~~~
foo.cc:42:7: 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:52:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 if (g == 0 && i >= s.size() && i >= b.s.size()) break;
               ~~^~~~~~~~~~~
foo.cc:52:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 if (g == 0 && i >= s.size() && i >= b.s.size()) break;
                                ~~^~~~~~~~~~~~~
foo.cc:54:7: 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:64:10: 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:64:34: 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:66:16: 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:127:19: 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:147:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d%d", &n, &m);
 ~~~~~^~~~~~~~~~~~~~~~
foo.cc:151:6: 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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