foo.cc: In function 'int main()':
foo.cc:9:13: warning: comparison between two arrays [-Warray-compare]
    9 |         if(n>=a){
      |            ~^~~
foo.cc:9:13: note: use unary '+' which decays operands to pointers or '&n[0] >= &a[0]' to compare the addresses
foo.cc:17:30: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
   17 |                 for(int i=1;i=r;i++)
      |                             ~^~

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