View Compilation Error

0_0_25779371_31911.cpp:5:1: error: 'ussing' does not name a type
 ussing namespace std;
 ^
0_0_25779371_31911.cpp:11:1: error: 'stack' does not name a type
 stack<char>st;
 ^
0_0_25779371_31911.cpp: In function 'int main()':
0_0_25779371_31911.cpp:28:22: error: 'st' was not declared in this scope
             else if(!st.empty()&&st.top()==sout[b])
                      ^