View Compilation Error

0_0_16923490_17987.cpp: In function 'node mul(node, node)':
0_0_16923490_17987.cpp:13:26: error: 'memset' was not declared in this scope
  memset(c.a,0,sizeof(c.a));
                          ^
0_0_16923490_17987.cpp: In function 'node pown(node, ll)':
0_0_16923490_17987.cpp:28:32: error: 'memset' was not declared in this scope
  memset(temp.a,0,sizeof(temp.a));
                                ^