View Compilation Error

0_0_36102456_7826.cpp: In function 'int main()':
0_0_36102456_7826.cpp:47:66: error: 'rand' was not declared in this scope
         if (minn < oldDis || exp((minn - oldDis) / step) > (rand() % 10000 / 10000.0)) {
                                                                  ^