foo.cc: In function 'int main()':
foo.cc:10:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   10 |     for(int i=0;i<a.size();i++)
      |                 ~^~~~~~~~~
foo.cc:22:36: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   22 |             if(a[i]=='('||a[i]==')'&&s1.top()==')')

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