foo.c: In function 'main':
foo.c:7:11: error: 'n' undeclared (first use in this function)
    7 |     int a[n];
      |           ^
foo.c:7:11: note: each undeclared identifier is reported only once for each function it appears in
foo.c:8:5: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
    8 |     for(int i=0;i<N;i++)
      |     ^~~
foo.c:10:9: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'for'
   10 |         for(int i=0;i<M;i++)
      |         ^~~
foo.c:7:9: warning: unused variable 'a' [-Wunused-variable]
    7 |     int a[n];
      |         ^

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