View Compilation Error

0_0_35980377_16559.cpp: In function 'node muti(node, node)':
0_0_35980377_16559.cpp:9:30: error: 'memset' was not declared in this scope
     memset(c.m, 0, sizeof c.m);
                              ^
0_0_35980377_16559.cpp: In function 'node pow_k(node, int)':
0_0_35980377_16559.cpp:18:34: error: 'memset' was not declared in this scope
     memset(ans.m, 0, sizeof ans.m);
                                  ^
0_0_35980377_16559.cpp: In function 'int main()':
0_0_35980377_16559.cpp:36:38: error: 'memset' was not declared in this scope
         memset(ans.m, 0, sizeof ans.m);
                                      ^