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#include<bits/stdc++.h>
#define FOR(i,a,b) for(int i=a;i<b;++i)
#define FOROP(i,a,b,op) for(int i=a;i<b;op)
#define FORD(i,a,b) for(int i=a;i>=b;--i)
#define PB push_back
#define FI first
#define SE second
#define umap unordered_map
#define uset unordered_set
#define vi vector<int>
#define vvi vector<vi>
#define pii pair<int, int>
#define ALL(X) (X).begin(),(X).end()
#ifndef DEBUG
#define endl (char)10
#endif
using namespace std;
using ll = long long;

#pragma optimize GCC ("Ofast")

int forbiden[5];
int n, m, k;
int sw[310];
int swcp[310];
int d[310];
vvi V(310);

int compute(){
    FOR(i,0,k){
        for(int x : V[forbiden[i]]){
            sw[x]--;
        }
        sw[forbiden[i]] = 494;
    }
    queue<int> q;
    int idx = 0;
    FOR(i,0,n){
        if (idx < k && forbiden[idx] == i){
            idx++;
            continue;
        }
        if (sw[i] == 0){
            q.push(i);
            d[i] = 1;
        }
    }
    while(!q.empty()){
        int t = q.front();
        q.pop();
        for(int x : V[t]){
            sw[x]--;
            d[x] = d[t] + 1;
            if (sw[x] == 0) q.push(x);
        }
    }
    int ans = 0;
    idx = 0;
    FOR(i,0,n){
        sw[i] = swcp[i];
        if (idx < k && forbiden[idx] == i){
            idx++;
            continue;
        }
        ans = max(ans, d[i]);
    }
    return ans;
}

int main () {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cin >> n >> m >> k;
    int p, q;
    FOR(i,0,310) sw[i] = 0;
    FOR(i,0,m){
        cin >> p >> q;
        p--;
        q--;
        sw[q]++;
        V[p].PB(q);
    }
    FOR(i,0,n) swcp[i] = sw[i];
    int ans = 1000000;
    if (k == 0){
        ans = compute();
    } else if (k == 1){
        FOR(i,0,n){
            forbiden[0] = i;
            ans = min(ans, compute());
        }
    } else if (k == 2){
        FOR(i,0,n){
            forbiden[0] = i;
            FOR(j,i+1,n){
                forbiden[1] = j;
                ans = min(ans, compute());
            }
        }
    } else if (k == 3){
        FOR(i,0,n){
            forbiden[0] = i;
            FOR(j,i+1,n){
                forbiden[1] = j;
                FOR(l,j+1,n){
                    forbiden[2] = l;
                    ans = min(ans, compute());
                }
            }
        }
    } else if (k == 4){
        FOR(i,0,n){
            forbiden[0] = i;
            FOR(j,i+1,n){
                forbiden[1] = j;
                FOR(l,j+1,n){
                    forbiden[2] = l;
                    FOR(s,l+1,n) {
                        forbiden[3] = s;
                        ans = min(ans, compute());
                    }
                }
            }
        }
    }
    cout << ans << endl;
}