View Compilation Error

0_0_16708394_20601.cpp: In function 'void init(long long int, long long int)':
0_0_16708394_20601.cpp:11:24: error: 'memset' was not declared in this scope
  memset(c, 0, sizeof(c));
                        ^
0_0_16708394_20601.cpp: In function 'int main()':
0_0_16708394_20601.cpp:33:31: error: 'memset' was not declared in this scope
   memset(mark, 0, sizeof(mark));
                               ^