foo.cc: In function 'int main()':
foo.cc:9:7: warning: comparison of constant '7' with boolean expression is always true [-Wbool-compare]
    9 |   1<=n<=7;
      |   ~~~~^~~
foo.cc:9:4: warning: comparisons like 'X<=Y<=Z' do not have their mathematical meaning [-Wparentheses]
    9 |   1<=n<=7;
      |   ~^~~
foo.cc:9:7: warning: statement has no effect [-Wunused-value]
    9 |   1<=n<=7;
      |   ~~~~^~~

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