g.cpp

#include <bits/stdc++.h>

using namespace std;

#define N 10010

typedef pair<int, int> ii;

void solve(int n)
{
    int inp[n + 1];
    for(int i = 1; i <= n; i++)
        scanf("%d", &inp[i]);
    // for(int i = 1; i <= n; i++)
        //printf("%d%c", inp[i], i == n ? '\n' : ' ');

    vector<int> g[N];
    int in[N] = {0};
    int out[N] = {0};
    for(int i = 1; i <= n; i++) {
        g[i].push_back(inp[i]);
        in[inp[i]]++;
        out[i]++;
    }
    
    vector<int> s;
    for(int i = 1; i <= n; i++) {
        if(in[i] == 0)
            s.push_back(i);
    }
    
    vector<ii> ans;
    for(int i = 0; i < (int) s.size(); i++) {
        int cnt = 0;
        int who = s[i];
        // printf("cnt %d who %d\n", cnt, who);
        while((int)g[who].size() > 0) {
            // printf("cnt %d who %d\n", cnt, who);
            cnt++;
            who = g[who][0];
        }

        ans.push_back(ii(s[i], cnt));
    }   
    sort(ans.begin(), ans.end());
    
    printf("%d", (int)ans.size());
    for(int i = 0; i < (int)ans.size(); i++)
        printf(" %d %d", ans[i].first, ans[i].second);
    printf("\n");
}

int main()
{
    int n;
    while(scanf("%d", &n) == 1 && n)
        solve(n);

    return 0;
}