View Compilation Error

0_0_19904705_32281.cpp: In function 'void prepare()':
0_0_19904705_32281.cpp:21:26: error: 'memset' was not declared in this scope
  memset(cnt,0,sizeof(cnt));
                          ^
0_0_19904705_32281.cpp: In function 'long long int dfs(int, int, int)':
0_0_19904705_32281.cpp:51:23: error: 'memset' was not declared in this scope
   memset(f,0,sizeof(f));
                       ^
0_0_19904705_32281.cpp: In function 'int main()':
0_0_19904705_32281.cpp:122:27: error: 'memset' was not declared in this scope
   memset(cnt,0,sizeof(cnt));
                           ^