foo.c: In function 'main':
foo.c:6:5: error: 'cin' undeclared (first use in this function)
    6 |     cin>>k;
      |     ^~~
foo.c:6:5: note: each undeclared identifier is reported only once for each function it appears in
foo.c:9:13: error: expected ';' before 's'
    9 |         n+=1
      |             ^
      |             ;
   10 |         s+=1.0/n;
      |         ~    
foo.c:14:13: error: expected ';' before '}' token
   14 |     return 0
      |             ^
      |             ;
   15 | }
      | ~            

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