foo.cc: In function 'int main()':
foo.cc:8:28: warning: iteration 6 invokes undefined behavior [-Waggressive-loop-optimizations]
    8 |             lesson[i] = a[i] + b[i];
      |                         ~~~^
foo.cc:7:23: note: within this loop
    7 |         for (i = 1; i <= 7; i++)
      |                     ~~^~~~

[Hydro](https://hydro.ac)提供评测服务