foo.cc:5:7: error: storage size of 'x' isn't known
    5 | int n,x[],y[],s1[],s2[];
      |       ^
foo.cc:5:11: error: storage size of 'y' isn't known
    5 | int n,x[],y[],s1[],s2[];
      |           ^
foo.cc:5:15: error: storage size of 's1' isn't known
    5 | int n,x[],y[],s1[],s2[];
      |               ^~
foo.cc:5:20: error: storage size of 's2' isn't known
    5 | int n,x[],y[],s1[],s2[];
      |                    ^~

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