//This is getting accepted!
#include<bits/stdc++.h>
#define pb push_back
#define mp make_pair
#define FI first
#define SE second
#define ll long long
#define oo 1000000009

using namespace std;

typedef pair<int, int> pii;
typedef vector<int> vi;
typedef long long lol;

const lol MOD = 1e9 + 7;
const double EPS = 1e-8;
const double PI = 2 * acos(0.0);
const int MAXN = 1e5 + 5;

int n;
int a[MAXN];
double p[MAXN];
double res;
bool vis[MAXN];
stack<int> sta;

int main(){
//    #ifndef ONLINE_JUDGE
//    freopen("inp.txt", "r", stdin);
//    freopen("out.txt", "w", stdout);
//    #endif
    scanf("%d", &n);
    for (int i = 0; i < n; ++i) {
    	scanf("%d%lf", a + i, p + i);	
    	--a[i];
    	p[i] /= 100;
    }
    
 	res = 0; 	
	memset(vis, 0, sizeof vis);
	for (int i = 0; i < n; ++i) {
		if (!vis[i]) {
			int u = i;			
			while (!vis[u]) {
				sta.push(u);
				vis[u] = true;
				u = a[u];
			}
			if (a[u] != -1) {
				double prob = 1;
				int v = u;
				do {
					prob = prob * p[v];
					v = a[v];
				} while (v != u);
				res = res + prob;
				u = i;				
			}
			while (!sta.empty()) {
				a[sta.top()] = -1;
				sta.pop();
			}
		}
	}
	printf("%.2lf", res);
	return 0;
}