foo.cc: In function 'int main()':
foo.cc:9:12: warning: comparison of constant '1000' with boolean expression is always true [-Wbool-compare]
    if (1<=x<=1000)
        ~~~~^~~~~~
foo.cc:9:9: warning: comparisons like 'X<=Y<=Z' do not have their mathematical meaning [-Wparentheses]
    if (1<=x<=1000)
        ~^~~

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