foo.cc: In function 'int main()':
foo.cc:5:2: error: 'scanf' was not declared in this scope
    5 |  scanf("%d",&n);
      |  ^~~~~
foo.cc:26:2: error: 'printf' was not declared in this scope
   26 |  printf("%d",k-1);
      |  ^~~~~~
foo.cc:2:1: note: 'printf' is defined in header '<cstdio>'; did you forget to '#include <cstdio>'?
    1 | #include <math.h>
  +++ |+#include <cstdio>
    2 | int main()
foo.cc:10:10: warning: unused variable 'k1' [-Wunused-variable]
   10 |  int k=0,k1=0;
      |          ^~

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