View Compilation Error

0_0_30640293_6285.cpp: In function 'int main()':
0_0_30640293_6285.cpp:13:21: error: no matching function for call to 'std::stack<char>::pop(char&)'
          st.pop(s[i]);
                     ^
0_0_30640293_6285.cpp:13:21: note: candidate is:
In file included from GCC4.9.2/x86_64-w64-mingw32/include/c++/stack:61:0,
                 from 0_0_30640293_6285.cpp:2:
GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/stl_stack.h:215:7: note: void std::stack<_Tp, _Sequence>::pop() [with _Tp = char; _Sequence = std::deque<char, std::allocator<char> >]
       pop()
       ^
GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/stl_stack.h:215:7: note:   candidate expects 0 arguments, 1 provided