View Compilation Error

0_0_17893444_13081.cpp:97:1: error: 'bitset' does not name a type
 bitset<MAXN/2>a[MAXN/2],in[MAXN/2],ans,nn;
 ^
0_0_17893444_13081.cpp: In function 'void init()':
0_0_17893444_13081.cpp:99:5: error: 'in' was not declared in this scope
     in[0].reset();
     ^
0_0_17893444_13081.cpp: In function 'int main()':
0_0_17893444_13081.cpp:135:9: error: 'nn' was not declared in this scope
         nn.reset();
         ^
0_0_17893444_13081.cpp:141:13: error: 'a' was not declared in this scope
             a[i]=nn;
             ^
0_0_17893444_13081.cpp:143:9: error: 'ans' was not declared in this scope
         ans.reset();
         ^
0_0_17893444_13081.cpp:150:20: error: 'a' was not declared in this scope
             ans|=((a[i]<<i)&(in[i+w]^in[i-1]));
                    ^
0_0_17893444_13081.cpp:150:30: error: 'in' was not declared in this scope
             ans|=((a[i]<<i)&(in[i+w]^in[i-1]));
                              ^