foo.cc: In function 'int main()':
foo.cc:41:19: error: 'j' was not declared in this scope
   41 |                 s[j] = s[j + 1];
      |                   ^
foo.cc:13:32: warning: unused variable 'flag' [-Wunused-variable]
   13 |     int leng = c.length(); int flag = 1;
      |                                ^~~~

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