foo.cc: In function 'void solve()':
foo.cc:8:9: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
    8 |     if(a=b*2)
      |        ~^~~~
foo.cc:14:23: error: lvalue required as left operand of assignment
   14 |     while(++i<--j&&i<b&&c[i]=c[j]);

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