foo.cc: In function 'int main()':
foo.cc:42:5: error: 'scanf_s' was not declared in this scope
     scanf_s("%d%d%d", &V, &M, &n);
     ^~~~~~~
foo.cc:42:5: note: suggested alternative: 'scanf'
     scanf_s("%d%d%d", &V, &M, &n);
     ^~~~~~~
     scanf

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。