View Compilation Error

0_0_20487438_23625.cpp: In function 'int main()':
0_0_20487438_23625.cpp:63:46: error: 'memset' was not declared in this scope
                    memset(mark,0,sizeof(mark));
                                              ^
0_0_20487438_23625.cpp:69:46: error: 'memset' was not declared in this scope
                    memset(mark,0,sizeof(mark));
                                              ^