foo.c: In function 'main':
foo.c:8:21: warning: comparison of constant '15' with boolean expression is always true [-Wbool-compare]
    8 |         for(n=1;1<=k<=15;n++){
      |                     ^~
foo.c:8:18: warning: comparisons like 'X<=Y<=Z' do not have their mathematical meaning [-Wparentheses]
    8 |         for(n=1;1<=k<=15;n++){
      |                 ~^~~

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