cf C. Tourist Problem
http://codeforces.com/contest/340/problem/C
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
1 #include <cstdio> 2 #include <cstring> 3 #include <algorithm> 4 #define maxn 100010 5 #define ll __int64 6 using namespace std; 7 8 ll a[maxn]; 9 int n; 10 11 ll gcd(ll a,ll b) 12 { 13 return b==0?a:gcd(b,a%b); 14 } 15 16 int main() 17 { 18 scanf("%d",&n); 19 ll ans=0; 20 for(int i=0; i<n; i++) 21 { 22 scanf("%I64d",&a[i]); 23 ans+=a[i]; 24 } 25 sort(a,a+n); 26 for(int i=1; i<=n-1; i++) 27 { 28 ans+=(a[i]-a[i-1])*i*(n-i)*2; 29 } 30 int k=gcd(ans,n); 31 printf("%I64d %I64d\n",ans/k,(ll)n/k); 32 return 0; 33 }