View Compilation Error

0_0_30051232_1708.cpp:12:1: error: 'stack' does not name a type
 stack<int>st;
 ^
0_0_30051232_1708.cpp: In function 'int main()':
0_0_30051232_1708.cpp:30:13: error: 'st' was not declared in this scope
             st.push(index);
             ^
0_0_30051232_1708.cpp:57:19: error: 'st' was not declared in this scope
             lst = st.top();
                   ^