View Compilation Error

0_0_21752791_9888.cpp:9:1: error: 'bitset' does not name a type
 bitset<1005>ok[11];
 ^
0_0_21752791_9888.cpp: In function 'int main()':
0_0_21752791_9888.cpp:16:7: error: 'ok' was not declared in this scope
       ok[i].reset();
       ^
0_0_21752791_9888.cpp:24:9: error: 'ok' was not declared in this scope
         ok[i][now] = 1;
         ^
0_0_21752791_9888.cpp:32:11: error: 'ok' was not declared in this scope
       if (ok[0][s[i] - '0'] && ok[n-1][s[i+n-1] - '0']){
           ^