/in/foo.cc: In function 'int main()':
/in/foo.cc:7:2: error: 'stack' was not declared in this scope
  stack<int>a;
  ^~~~~
/in/foo.cc:7:8: error: expected primary-expression before 'int'
  stack<int>a;
        ^~~
/in/foo.cc:8:8: error: expected primary-expression before 'char'
  stack<char>b;
        ^~~~
/in/foo.cc:9:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<m.size();i++)
              ~^~~~~~~~~
/in/foo.cc:13:4: error: 'a' was not declared in this scope
    a.push(m[i]-'0');
    ^
/in/foo.cc:17:7: error: 'a' was not declared in this scope
    if(a.size()<2)
       ^
/in/foo.cc:22:10: error: 'a' was not declared in this scope
    int x=a.top();
          ^
/in/foo.cc:41:8: error: 'a' was not declared in this scope
  cout<<a.top();
        ^