#include <bits/stdc++.h>
#define LL long long
using namespace std;
double ans=0.0;
int n,to[100005];
double prob[100005];
int vis[100005];
int main(){
	scanf("%d",&n);
	for(int i=1;i<=n;i++){
		int a,b;
		scanf("%d %d",&a,&b);
		to[i]=a;
		prob[i]=b/100.0;
	}
	memset(vis,0,sizeof(vis));
	for(int i=1;i<=n;i++){
		if(vis[i]==0){
			int cur=i;
			while(vis[cur]==0){
				vis[cur]=1;
				cur=to[cur];
			}
			while(vis[cur]==1){
				vis[cur]=2;
				cur=to[cur];
			}
			cur=i;
			while(vis[cur]==1){
				vis[cur]=3;
				cur=to[cur];
			}
		}
	}
	for(int i=1;i<=n;i++){
		double a=1.0;
		int cur=i;
		if(vis[cur]!=2) continue;
		while(vis[cur]==2){
			vis[cur]=3;
			a=a*prob[cur];
			cur=to[cur];
		}
		ans+=a;
	}
	printf("%.2lf\n",ans);
	return 0;
}