foo.cc: In function 'int f(int)':
foo.cc:8:26: warning: iteration 6999 invokes undefined behavior [-Waggressive-loop-optimizations]
    8 |                 if(a[k][i])
      |                    ~~~~~~^
foo.cc:7:22: note: within this loop
    7 |         for(int i=1;i<=7000;i++)
      |                     ~^~~~~~

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