#pragma region template
#include<bits/stdc++.h>
using namespace std;
//other
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>

// using namespace __gnu_pbds;
#include<atcoder/all>
using namespace atcoder;
// #include "atcoder/modint.hpp"
using mint = atcoder::modint998244353;
using zint = atcoder::modint1000000007;
// using mint=modint;
#define int long long
#define pb push_back
#define eb emplace_back
#define ep emplace
#define len(a) (int)a.size()
#define BIT(a,b) ((a)>>(b)&1)
// #define endl "\n"

// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

//using 
using ll=long long;
using i32=signed;
using i64=long long;
using i128=__int128_t;
using ld=long double;
using ull=unsigned long long;
using uint=unsigned;
using pcc=pair<char,char>;
using pii=pair<int,int>;
using pll=pair<ll,ll>;
using pdd=pair<ld,ld>;
using vi=vector<int>;
using vl=vector<ll>;
using vvi=vector<vi>;
using vvl=vector<vl>;
using vvvi=vector<vvi>;
using vvvl=vector<vvl>;
template<class T>using V=vector<T>;
template<class T>using VV=vector<V<T>>;
template<class T>using VVV=vector<VV<T>>;
template<class T>using VVVV=vector<VVV<T>>;
template<class T>using VVVVV=vector<VVVV<T>>;
template<class T>using pqmin=priority_queue<T,vector<T>,greater<T>>;
template<class T>using pqmax=priority_queue<T>;
// template<class T>using pbds=tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

#define chmax(a,b) (a)=max((a),(b))
#define chmin(a,b) (a)=min((a),(b))

const ll LINF=0x1fffffffffffffff;
const int INF=0x3fffffff;
const int MOD=998244353;
const int MOD2=1000000007;
const ld PI=3.1415926535897932384626433832795028841971;
const ld DINF=numeric_limits<ld>::infinity();
const ld EPS=1e-9;
const ll di[]={0,1,0,-1,1,-1,1,-1};
const ll dj[]={1,0,-1,0,1,1,-1,-1};

template<class T>
constexpr auto min(T a,T b,T c){
    return min(a,min(b,c));
}
template<class... T>
constexpr auto min(T... a){
    return min(initializer_list<common_type_t<T...>>{a...});
}

template<class T>
constexpr auto max(T a,T b,T c){
    return max(a,max(b,c));
}

template<class... T>
constexpr auto max(T... a){
    return max(initializer_list<common_type_t<T...>>{a...});
}

#define overload4(_1,_2,_3,_4,name,...) name
#define overload3(_1,_2,_3,name,...) name

#define rep1(n) for(ll i=0;i<n;++i)
#define rep2(i,n) for(ll i=0;i<n;++i)
#define rep3(i,a,b) for(ll i=a;i<b;++i)
#define rep4(i,a,b,c) for(ll i=a;i<b;i+=c)
#define rep(...) overload4(__VA_ARGS__,rep4,rep3,rep2,rep1)(__VA_ARGS__)

#define rrep1(n)for(ll i=n;i--;)
#define rrep2(i,n)for(ll i=n;i--;)
#define rrep3(i,a,b)for(ll i=b;i-->(a);)
#define rrep4(i,a,b,c)for(ll=(a)+((b)-(a)-1)/(c)*(c);i>=(a);i-=c)
#define rrep(...) overload4(__VA_ARGS__,rrpe4,rrep3,rrep2,rrep1)(__VA_ARGS__)

#define isum(...) accumulate(all(__VA_ARGS__),0LL)
#define dsum(...) accumulate(all(__VA_ARGS__),0.0L)
#define Msum(...) accumulate(all(__VA_ARGS__),0_M)
#define elif else if

#define INT(...) int __VA_ARGS__;input(__VA_ARGS__)
#define LL(...) ll __VA_ARGS__;input(__VA_ARGS__)
#define ULL(...) ull __VA_ARGS__;input(__VA_ARGS__)
#define STR(...) string __VA_ARGS__;input(__VA_ARGS__)
#define CHR(...) char __VA_ARGS__;input(__VA_ARGS__)
#define DBL(...) double __VA_ARGS__;input(__VA_ARGS__)
#define LD(...) ld __VA_ARGS__;input(__VA_ARGS__)

//io
//in
void scan(){}
void scan(signed &a){cin>>a;}
void scan(unsigned &a){cin>>a;}
void scan(long& a){cin>>a;}
void scan(long long& a){cin>>a;}
void scan(unsigned long long&a){cin>>a;}
void scan(char& a){cin>>a;}
void scan(float& a){cin>>a;}
void scan(double& a){cin>>a;}
void scan(long double& a){cin>>a;}
void scan(vector<bool>& a){ for(unsigned i = 0; i < a.size(); i++){ int b; scan(b); a[i] = b; } }
void scan(char a[]){ scanf("%s", a); }
void scan(string& a){cin>>a;}
template<class T> void scan(vector<T>&);
template<class T, int size> void scan(array<T, size>&);
template<class T, class L> void scan(pair<T, L>&);
template<class T, int size> void scan(T(&)[size]);
template<class T> void scan(vector<T>& a){ for(auto&& i : a) scan(i); }
template<class T> void scan(deque<T>& a){ for(auto&& i : a) scan(i); }
template<class T, int size> void scan(array<T, size>& a){ for(auto&& i : a) scan(i); }
template<class T, class L> void scan(pair<T, L>& p){ scan(p.first); scan(p.second); }
template<class T, int size> void scan(T (&a)[size]){ for(auto&& i : a) scan(i); }
template<class T> void scan(T& a){ cin >> a; }
void input(){}
template<class Head,class...Tail> void input(Head& head,Tail&... tail){scan(head);input(tail...);}
//out
void puts(){ putchar(' '); }
void puts(bool a){ printf("%d", a); }
void puts(signed a){ printf("%d", a); }
void puts(unsigned a){ printf("%u", a); }
void puts(long a){ printf("%ld", a); }
void puts(long long a){ printf("%lld", a); }
void puts(unsigned long long a){ printf("%llu", a); }
void puts(char a){ printf("%c", a); }
void puts(char a[]){ printf("%s", a); }
// void puts(const char a[]){ printf("%s", a); }
void puts(float a){ printf("%.15f", a); }
void puts(double a){ printf("%.15f", a); }
void puts(long double a){ printf("%.15Lf", a); }
void puts(const string& a){ for(auto&& i : a) puts(i); }
template<class T> void puts(const complex<T>& a){ if(a.real() >= 0) puts('+'); puts(a.real()); if(a.imag() >= 0) puts('+'); puts(a.imag()); puts('i'); }
template<class T> void puts(const vector<T>&);
template<class T, int size> void puts(const array<T, size>&);
template<class T, class L> void puts(const pair<T, L>& p);
template<class T, int size> void puts(const T (&)[size]);
template<class T> void puts(const vector<T>& a){ if(a.empty()) return; puts(a[0]); for(auto i = a.begin(); ++i != a.end(); ){ putchar(' '); puts(*i); } }
template<class T> void puts(const deque<T>& a){ if(a.empty()) return; puts(a[0]); for(auto i = a.begin(); ++i != a.end(); ){ putchar(' '); puts(*i); } }
template<class T> void puts(const set<T>& a){ if(a.empty()) return; puts(*a.begin()); for(auto i = a.begin(); ++i != a.end(); ){ putchar(' '); puts(*i); } }
template<class T> void puts(const multiset<T>& a){ if(a.empty()) return; puts(*a.begin()); for(auto i = a.begin(); ++i != a.end(); ){ putchar(' '); puts(*i); } }
template<class T, int size> void puts(const array<T, size>& a){ puts(a[0]); for(auto i = a.begin(); ++i != a.end(); ){ putchar(' '); puts(*i); } }
template<class T, class L> void puts(const pair<T, L>& p){ putchar('(');puts(p.first); putchar(' '); puts(p.second); putchar(')');}
template<class T, int size> void puts(const T (&a)[size]){ puts(a[0]); for(auto i = a; ++i != end(a); ){ putchar(' '); puts(*i); } }
template<class T> void puts(const T& a){ cout << a; }
int print(){ putchar('\n'); return 0; }
template<class T> int print(const T& t){ puts(t); putchar('\n'); return 0; }
template<class Head, class... Tail> int print(const Head& head, const Tail&... tail){ puts(head); putchar(' '); print(tail...); return 0; }
#pragma endregion

#pragma region commonly used
int digitsum(string s){
    int res=0;
    rep(i,(int)s.size()){
        res+=s[i]-'0';
    }
    return res;
}

//乱数系
random_device rnd; 
mt19937 mt(rnd());
const long long MT_MAX=LINF;
uniform_int_distribution<long long> rd(0,MT_MAX);
double randd(){
    return 1.0*rd(mt)/MT_MAX;
}
long long randint(long long a,long long b){
    // [a,b]の乱数を生成
    return a+rd(mt)%(b-a+1);
}

std::ostream &operator<<(std::ostream &dest, __int128_t value) {
    std::ostream::sentry s(dest);
    if (s) {
        __uint128_t tmp = value < 0 ? -value : value;
        char buffer[128];
        char *d = std::end(buffer);
        do {
            --d;
            *d = "0123456789"[tmp % 10];
            tmp /= 10;
        } while (tmp != 0);
        if (value < 0) {
            --d;
            *d = '-';
        }
        int len = std::end(buffer) - d;
        if (dest.rdbuf()->sputn(d, len) != len) {
            dest.setstate(std::ios_base::badbit);
        }
    }
    return dest;
}

__int128 parse(string &s) {
    __int128 ret = 0;
    for (int i = 0; i < (int)s.length(); i++)
        if ('0' <= s[i] && s[i] <= '9')
        ret = 10 * ret + s[i] - '0';
    return ret;
}


// #include<boost/multiprecision/cpp_int.hpp>
// using lint=boost::multiprecision::cpp_int;

#pragma endregion

vector<int> dijkstra(vector<vector<pair<int,int>>> &g,int start){
    priority_queue<pair<int,int>,vector<pair<int,int>>,greater<pair<int,int>>> q;
    vector<bool> kakutei(g.size(),false);
    vector<int> dis(g.size(),(int)1e15);
    q.push(make_pair(0,start));
    dis[start]=0;
    while(!q.empty()){
        pair<int,int> p=q.top();q.pop();
        int pos=p.second,cost=p.first;
        if(kakutei[pos])continue;
        kakutei[pos]=true;
        for(auto nex:g[pos]){
            int npos=nex.first,ncos=nex.second;
            if(dis[npos]>cost+ncos){
                dis[npos]=cost+ncos;
                q.push(make_pair(dis[npos],npos));
            }
        }
    }
    return dis;
}

signed main(){
    
    INT(n,m);
    INT(s,t,k);s--;t--;
    VV<pair<int,int>> g(n);
    rep(i,m){
        INT(a,b);a--;b--;
        g[a].pb({b,1});
        g[b].pb({a,1});
    }
    auto d=dijkstra(g,s);
    // print(d);
    cout<<"Unknown"<<endl;
    return 0;
    if(d[t]==1e15){
        cout<<"Unknown"<<endl;
        return 0;
    }
    if(d[t]%2!=k%2){
        cout<<"No"<<endl;
        return 0;
    }
    if(d[t]<=k){
        cout<<"Yes"<<endl;
        return 0;
    }
    cout<<"Unknown"<<endl;
}