View Compilation Error

0_0_39410707_2030.cpp: In function 'int main()':
0_0_39410707_2030.cpp:21:17: error: 'memset' was not declared in this scope
   21 |                 memset(pre, 0, sizeof(pre));
      |                 ^~~~~~
0_0_39410707_2030.cpp:4:1: note: 'memset' is defined in header '<cstring>'; did you forget to '#include <cstring>'?
    3 | #include <algorithm>
  +++ |+#include <cstring>
    4 | typedef long long ll;