foo.cc: In function 'int main()':
foo.cc:33:8: warning: array subscript has type 'char' [-Wchar-subscripts]
   33 |   if(c[k]!=0)f=1;
      |        ^
foo.cc:34:19: warning: array subscript has type 'char' [-Wchar-subscripts]
   34 |   if(f==1)cout<<c[k];
      |                   ^

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