#include <bits/stdc++.h>
#define ll long long
#define mp make_pair
#define fi first
#define se second
#define pb push_back
#define vi vector<int>
#define pi pair<int, int>
#define mod 998244353
template<typename T> bool chkmin(T &a, T b){return (b < a) ? a = b, 1 : 0;}
template<typename T> bool chkmax(T &a, T b){return (b > a) ? a = b, 1 : 0;}
ll ksm(ll a, ll b) {if (b == 0) return 1; ll ns = ksm(a, b >> 1); ns = ns * ns % mod; if (b & 1) ns = ns * a % mod; return ns;}
using namespace std;
const int maxn = 100005;

int n, m, k;
int tp[maxn];
ll dis[maxn];
int t[maxn];
vi eg[maxn];
priority_queue<pair<ll, int > > q;
int main() {
    cin >> n >> m >> k;
    for (int i = 1; i <= n; i++)
        cin >> t[i];
    int flag = 0;
    for (int i = 1; i <= m; i++) {
        int u, v;
        cin >> u >> v;
        if (min(u, v) == 1 && max(u, v) == n) flag = 1;
        eg[u].pb(v);
        eg[v].pb(u);
    }
    const ll inf = 1e18;
    for (int i = 0; i <= n; i++)
        dis[i] = inf;
    dis[1] = 0;
    q.push(mp(0, 1));
    while (!q.empty()) {
        auto [d, id] = q.top(); q.pop();
        if (d != -dis[id]) continue;
        for (auto v : eg[id]) 
            if (chkmin(dis[v], dis[id] + t[v])) 
                q.push(mp(-dis[v], v));
    }
    if (flag) {
        if (n == 2 && k == 1) {
            cout << "impossible" << endl;
            return 0;
        }
        else {
            int rev = 0;
            if (k < 2) rev = 1, k = n - k;
            tp[1] = tp[n] = 0; k -= 2;
            for (int j = 2; j <= k + 1; j++) tp[j] = 0;
            for (int j = k + 2; j < n; j++) tp[j] = 1;
            if (rev) 
                for (int j = 1; j <= n; j++) tp[j] ^= 1;
        }
    }
    else {
        vector<pair<ll, int> > cr;
        for (int i = 1; i <= n; i++)
            cr.pb(mp(dis[i], i));
        sort(cr.begin(), cr.end());
        for (int j = 0; j < k; j++)
            tp[cr[j].se] = 0;
        for (int j = k; j < n; j++)
            tp[cr[j].se] = 1;
    }
    for (int i = 1; i <= n; i++)
        cout << (tp[i] ? 'S' : 'N'); cout << endl;
    return 0;
}