学步园

#include<bits/stdc++.h>
int n,A,B,C,a[10000001];
double ans;
int main(){
	scanf("%d%d%d%d%d",&n,&A,&B,&C,a+1); 
	for(int i=2;i<=n;i++)a[i]=((long long)a[i-1]*A+B)%100000001; 
	for(int i=1;i<=n;i++)a[i]=a[i]%C+1;
	for(int i=1;i<n;i++)ans+=1.0/(a[i]>a[i+1]?a[i]:a[i+1]);
	printf("%.3lf",ans+1.0/(a[n]>a[1]?a[n]:a[1]));
	return 0;
}