#include <bits/stdc++.h>
using namespace std;


int w[100000];
long double prob[100000];
int vis[100000];

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);

    int n; cin >> n;
    for (int i = 0; i < n; ++i)
        cin >> w[i] >> prob[i], --w[i], prob[i] /= 100.0;
    
    long double ans = 0.0;
    for (int i = 0; i < n; ++i) {
        if (vis[i])
            continue;
        int cur = i;
        while(!vis[cur])
            vis[cur] = i + 1, cur = w[cur];
        if (vis[cur] != i + 1)
            continue;
        long double thisCycle = 1.0;
        int cur2 = cur;
        do {
            thisCycle *= prob[cur2];
            cur2 = w[cur2];
        } while(cur != cur2);
        ans += thisCycle;
    }

    cout << fixed << setprecision(2) << ans;
    return 0;
}