foo.cc: In function 'int main()':
foo.cc:7:11: error: expected ';' before '>=' token
    7 |  for(int n>=100&&n<=999)
      |           ^~
      |           ;
foo.cc:7:11: error: expected primary-expression before '>=' token
    7 |  for(int n>=100&&n<=999)
      |           ^~
foo.cc:7:24: error: expected ';' before ')' token
    7 |  for(int n>=100&&n<=999)
      |                        ^
      |                        ;
foo.cc:9:4: warning: statement has no effect [-Wunused-value]
    9 |   x+10*(n%10);
      |   ~^~~~~~~~~~

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