foo.cc: In function 'int main()':
foo.cc:23:5: error: 'memset' was not declared in this scope
   23 |     memset(f,1,sizeof(f));
      |     ^~~~~~
foo.cc:4:1: note: 'memset' is defined in header '<cstring>'; did you forget to '#include <cstring>'?
    3 | #include <algorithm>
  +++ |+#include <cstring>
    4 | #define ll long long
foo.cc:22:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   22 |     scanf("%d%d%d%d",&n,&m,&row,&col);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

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