AC了

#include<bits/stdc++.h>
#define ll long long
#pragma GCC optimize(2)
#define un unsigned
#define int long long
#define db double
#define inf 1000000000000000
#define st string
#define ct const
#define xh(a,b,c) for(int a=b;a<=c;a++)
#define wx while(1)
#define dn(a,b,c) for(int a=b;a>=c;a--)
using namespace std;
int n,a[100010],b[100010],ans;
void qsort(int left,int right){
	int mid=(left+right)/2;
	if(left>=right)return ;
	int k=left,i=left,j=mid+1;
	qsort(left,mid);
	qsort(mid+1,right);
	while(i<=mid&&j<=right){
		if(a[i]<a[j]){
			ans+=mid-i+1;
			b[k++]=a[j++];
		}
		else b[k++]=a[i++];
	}
	while(i<=mid)b[k++]=a[i++];
	while(j<=right)b[k++]=a[j++];
	xh(i,left,right)a[i]=b[i];
}
signed main(){
	cin>>n;
	xh(i,1,n)cin>>a[i],a[i]+=(n-i+1);//重点
	qsort(1,n);
	cout<<ans%12345;
	return 0;
}