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Feb 17th, 2018
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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. typedef long long ll;
  4. const int MAX_N = 1e6+10;
  5. const int mod = 1e9+7;
  6.  
  7. ll a[MAX_N],n,fact[MAX_N],rfact[MAX_N];
  8. ll num(int t){
  9. return fact[n-t-1]*rfact[n-t+1]%mod;
  10. }
  11. main(){
  12. scanf("%lld", &n);
  13. for(ll i=1;i<=n;i++)
  14. scanf("%lld", &a[i]);
  15. fact[0]=rfact[n+1]=1;
  16. for(int i=1;i<=n+1;i++)
  17. fact[i]=(fact[i-1]*i)%mod;
  18. for(int i=n;i>=1;i--)
  19. rfact[i]=(rfact[i+1]*i)%mod;
  20. sort(a+1,a+n+1);
  21. ll cnt=0,curr=0,ans=0;
  22. for(ll i=1;i<=n&&a[i]!=a[n];i++){
  23. if(a[i]==a[i-1])
  24. cnt++;
  25. else
  26. curr+=cnt,cnt=1;
  27. ans=(ans+num(curr)*a[i]%mod)%mod;
  28. }
  29. printf("%d",ans);
  30. }
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