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#include <bits/stdc++.h>

#define forn(i, n) for(int i = 0; i < n; ++i)

using namespace std;

typedef long long LL;
typedef pair<int, int> pint;

int n,m,k;
vector<int> nbh[342];
set<int> inverts[342];
int mincmp = 1000000;

set<vector<int>> was;

int cmp[342];
int par[342];
int indeg[342];

void bfs(int v1, int v2, int v3, int v4)
{
    queue<int> Q;
    for (int i=1; i<=n; i++)
    {
        if (i == v1 || i == v2 || i == v3 || i == v4)
        {
            par[i] = -1;
            cmp[i] = 0;
            continue;
        }
        par[i] = -1;
        cmp[i] = 1;

        int s = inverts[i].size();
        s -= (inverts[i].find(v1) != inverts[i].end());
        s -= (inverts[i].find(v2) != inverts[i].end());
        s -= (inverts[i].find(v3) != inverts[i].end());
        s -= (inverts[i].find(v4) != inverts[i].end());

        if (s == 0)
            Q.push(i);
        indeg[i] = s;
    }

    while (!Q.empty())
    {
        int a = Q.front();
        Q.pop();
        for (int v : nbh[a])
        {
            if (v == v1 || v == v2 || v == v3 || v == v4)
                continue;

            indeg[v]--;
            cmp[v] = max(cmp[v],cmp[a]+1);
            if (indeg[v] == 0)
            {
                par[v] = a;
                Q.push(v);
            }
        }
    }
}

void solve(int k, int v1 = -1, int v2 = -1, int v3 = -1, int v4 = -1)
{
    vector<int> vv = {v1,v2,v3,v4};
    sort(vv.begin(),vv.end());

    if (was.find(vv) != was.end())
        return;
    was.insert(vv);

    bfs(v1,v2,v3,v4);

    if (k == 0)
    {
        int maxcmp = 0;
        for (int i=1; i<=n; i++)
        {
            if (maxcmp < cmp[i] && i != v1 && i != v2 && i != v3 && i != v4)
                maxcmp = cmp[i];
        }
        mincmp = min(mincmp, maxcmp);
        return;
    }


    int vmaxcmp = 0;
    for (int i=1; i<=n; i++)
    {
        if (cmp[i] > cmp[vmaxcmp])
            vmaxcmp = i;
    }

    if (cmp[vmaxcmp] < mincmp)
        mincmp = cmp[vmaxcmp];

    vector<int> to_erase;
    while (vmaxcmp != -1)
    {
        to_erase.push_back(vmaxcmp);
        vmaxcmp = par[vmaxcmp];
    }

    for (int v : to_erase)
    {
        if (v1 == -1)
            solve(k-1, v);
        else if (v2 == -1)
            solve(k-1, v1, v);
        else if (v3 == -1)
            solve(k-1, v1, v2, v);
        else 
            solve(k-1, v1, v2, v3, v);
    }
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    
    cin >> n >> m >> k;
    for (int i=0; i<m; i++)
    {
        int x,y;
        cin >> x >> y;
        nbh[x].push_back(y);
        inverts[y].insert(x);
    }

    solve(k);
    cout << mincmp;

    
    return 0;
}