foo.cc: In function 'int main()':
foo.cc:8:7: error: 'i' was not declared in this scope
    8 |   for(i=1;i<=n;i++)
      |       ^
foo.cc:19:9: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
   19 |   if(sum=n)
      |      ~~~^~

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