Main.cc: In function ‘int main()’: Main.cc:41:31: error: ‘mod’ was not declared in this scope add(ans,1ll*check(i,k/i)%mod); ^~~ Main.cc:41:31: note: suggested alternative: ‘modf’ add(ans,1ll*check(i,k/i)%mod); ^~~ modf Main.cc:28:10: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d",&n,&m,&k); ~~~~~^~~~~~~~~~~~~~~~~~~ Main.cc:30:14: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&a[i]); ~~~~~^~~~~~~~~~~~ Main.cc:35:14: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&b[i]); ~~~~~^~~~~~~~~~~~