View Compilation Error

0_0_27310818_12488.cpp: In function 'int main()':
0_0_27310818_12488.cpp:19:33: error: 'pow' was not declared in this scope
    if (2 * ans[j] + pow(2, i - j) - 1 < mm) mm = 2 * ans[j] + (int)pow(2, i - j) - 1;
                                 ^