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#include <iostream>
#include <cstdio>
#include <string>
#include <sstream> 
#include <vector>
#include <map>
#include <set>
#include <cmath>
#include <algorithm>
using namespace std;
const int INF = 1e9;
const int N = 1e3;
const int MAX_CANDIDATES = 90;

vector<int> g[N];
int dp[N];
int dp_from[N];

void print(const vector<int>& chain) {
    cout << "len=" << chain.size() << "; ";
    for (auto v : chain) {
        cout << v+1 << ",";
    }
    cout << endl;
}


void dfs_max_len_candidates(int v, int rem_len, set<int>& candidates_set, vector<int>& path, int limit) {
    path.push_back(v);
    if (rem_len == 1) {
        for (auto v : path) {
            if (candidates_set.size() >= limit) break;
            candidates_set.insert(v);
        }
    } else {
        for (auto u : g[v]) {
            if (candidates_set.size() >= limit) break;
            if (dp[u] == rem_len-1) {
                dfs_max_len_candidates(u, rem_len-1, candidates_set, path, limit);
            }
        }
    }
    path.pop_back();
}
void dfs_candidates(int v, int rem_len, set<int>& candidates_set, vector<int>& path, const set<int>& candidates_max_len_set, int limit) {
    path.push_back(v);
    if (rem_len == 1) {
        for (auto v : path) {
            if (candidates_set.size() >= limit) break;
            if (candidates_max_len_set.find(v) == candidates_max_len_set.end()) {
                candidates_set.insert(v);
            }
        }
    } else {
        for (auto u : g[v]) {
            if (candidates_set.size() >= limit) break;
            if (dp[u] == rem_len-1) {
                dfs_candidates(u, rem_len-1, candidates_set, path, candidates_max_len_set, limit);
            }
        }
    }
    path.pop_back();
}

int main() {
    int n, m, k;
    scanf("%d %d %d", &n, &m, &k);
    for (int i = 0; i < m; ++i) {
        int u, v;
        scanf("%d %d", &u, &v);
        --u, --v;
        g[u].push_back(v);
    }
    for (int v = n-1; v >= 0; --v) {
        dp[v] = 1;
        for (auto u : g[v]) {
            dp[v] = max(dp[v], dp[u] + 1);
        }
        dp_from[v] = max(dp[v], dp_from[v+1]);
    }
    int max_len = 0;
    for (int v = 0; v < n; ++v) {
        max_len = max(max_len, dp[v]);
    }
    if (k == 0) {
        printf("%d\n", max_len);
        return 0;
    }

    //cerr << "max_len=" << max_len << endl;
    int num_chains = 0;
    set<int> candidates_max_len_set;
    set<int> candidates_set;

    for (int v = 0; v < n; ++v) {
        if (dp[v] == max_len) {
            vector<int> path;
            dfs_max_len_candidates(v, max_len, candidates_max_len_set, path, MAX_CANDIDATES);
        }
    }

    for (int len = max_len-1; len >= 1; --len) {
        if (candidates_max_len_set.size() + candidates_set.size() >= MAX_CANDIDATES) break;
        for (int v = 0; v < n; ++v) {
            if (candidates_max_len_set.size() + candidates_set.size() >= MAX_CANDIDATES) break;
            if (dp[v] == len) {
                vector<int> path;
                dfs_candidates(v, len, candidates_set, path, candidates_max_len_set, MAX_CANDIDATES-(int)candidates_max_len_set.size());
            }
        }
    }
    vector<int> candidates_max_len(candidates_max_len_set.rbegin(), candidates_max_len_set.rend());
    vector<int> candidates(candidates_set.rbegin(), candidates_set.rend());

    for (auto max_candidate : candidates_max_len) {
        candidates.push_back(max_candidate);
    }

    /*
    cerr << "num_candidates_max_len=" << candidates_max_len.size() << endl;
    cerr << "num_candidates=" << candidates.size() << endl;
    */

    vector<vector<int>> tuples;
    if (k == 1) {
        for (auto v : candidates_max_len) {
            tuples.push_back({v});
        }
    } else if (k == 2) {
        for (auto v : candidates_max_len) {
            for (int i1 = 0; i1 < candidates.size(); ++i1) {
                int x1 = candidates[i1];
                if (x1 == v) continue;
                tuples.push_back({v, x1});
            }
        }
    } else if (k == 3) {
        for (auto v : candidates_max_len) {
            for (int i1 = 0; i1 < candidates.size(); ++i1) {
                int x1 = candidates[i1];
                if (x1 == v) continue;
                for (int i2 = i1+1; i2 < candidates.size(); ++i2) {
                    int x2 = candidates[i2];
                    if (x2 == v) continue;
                    tuples.push_back({v, x1, x2});
                }
            }
        }
    } else if (k == 4) {
        for (auto v : candidates_max_len) {
            for (int i1 = 0; i1 < candidates.size(); ++i1) {
                int x1 = candidates[i1];
                if (x1 == v) continue;
                for (int i2 = i1+1; i2 < candidates.size(); ++i2) {
                    int x2 = candidates[i2];
                    if (x2 == v) continue;
                    for (int i3 = i2+1; i3 < candidates.size(); ++i3) {
                        int x3 = candidates[i3];
                        if (x3 == v) continue;
                        tuples.push_back({v, x1, x2, x3});
                    }
                }
            }
        }
    }

    for (auto& tuple : tuples) {
        sort(tuple.begin(), tuple.end(), greater<int>());
    }
    /*
    cerr << "num_tuples=" << tuples.size() << endl;
    cerr << "tuple iteration..." << endl;
    */
    int res = max_len;

    vector<int> mem(n, 0);
    int last_computed = n;
    int tail_len = 0;
    for (const auto& tuple : tuples) {
        // loop over all but last vertices
        int tuple_mx = tuple[0];
        for (int v = tuple_mx+1; v < last_computed; ++v) {
            mem[v] = dp[v];
            tail_len = max(tail_len, dp[v]);
        }
        last_computed = tuple_mx+1;
        for (auto v : tuple) {
            mem[v] = 0;
        }
        int len = tail_len;
        for (int idx = 0; idx < tuple.size(); ++idx) {
            int ma = tuple[idx]-1;
            int mi = idx+1 == tuple.size() ? 0 : tuple[idx+1]+1;

            for (int v = ma; v >= mi; --v) {
                mem[v] = 1;
                for (auto u : g[v]) {
                    mem[v] = max(mem[v], mem[u] + 1);
                }
                len = max(len, mem[v]);
            }
        }
        res = min(res, len);
        for (auto v : tuple) {
            mem[v] = dp[v];
        }
    }
    printf("%d\n", res);
    return 0;
}