foo.cc:3:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
    3 | main()
      |      ^
foo.cc: In function 'int main()':
foo.cc:8:3: error: 'cin' was not declared in this scope
    8 |   cin>>n;
      |   ^~~
foo.cc:2:1: note: 'std::cin' is defined in header '<iostream>'; did you forget to '#include <iostream>'?
    1 | #include<stdio.h>
  +++ |+#include <iostream>
    2 | using namespace std;

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