#include<cstdio>
#include<iostream>
#include<queue>
using namespace std;
namespace LZZMD{
	const int N = 1e5, M = 2e5, inf = 0x7fffffff / 2;
	struct edge{
		int nxt, to;
	} e[M * 6 + 10];
	int head[N * 3 + 10], cnt;
	int time[N + 10];
	int n, m, k;
	inline void add(int u, int v){
		e[++cnt] = {head[u], v};
		head[u] = cnt;
	}
	struct node{
		int u, dis;
	};
	priority_queue<node> q;
	bool operator < (node x, node y){
		return x.dis > y.dis;
	}
	int dis[N + 10], vis[N + 10];
	inline void dijkstra(int s){
		for(int i = 1; i <= n; i++)
			dis[i] = inf;
		dis[s] = time[s];
		q.push({s, dis[s]});
		while(q.size()){
			int u = q.top().u;
			q.pop();
			if(vis[u])
				continue;
			vis[u] = 1;
			for(int i = head[u]; i; i = e[i].nxt){
				int v = e[i].to;
				if(dis[v] > dis[u] + time[v]){
					dis[v] = dis[u] + time[v];
					q.push({v, dis[v]});
				}
			}
		}
	}
	int rd[N + 10], que[N + 10], f[N + 10][2];
	bool ans[N + 10], ans1 = true, ans2 = false;
	void print(int u){
		if(f[u - 2 * n][0] <= f[u - 2 * n][1]){
			ans[u - 2 * n] = ans2;
			for(int i = head[u]; i; i = e[i].nxt)
				print(e[i].to);
		}
		else{
			ans[u - 2 * n] = ans1;
			for(int i = head[u]; i; i = e[i].nxt)
				ans[e[i].to - 2 * n] = ans1;
		}
	}
	int main(){
		scanf("%d%d%d", &n, &m, &k);
		for(int i = 1; i <= n; i++)
			scanf("%d", &time[i]);
		for(int i = 1, u, v; i <= m; i++){
			scanf("%d%d", &u, &v);
			add(u, v), add(v, u);
		}
		dijkstra(1);
		for(int u = 1; u <= n; u++)
			for(int i = head[u]; i; i = e[i].nxt)
				if(dis[e[i].to] + time[u] == dis[u])
					add(e[i].to + n, u + n), add(u + 2 * n, e[i].to + 2 * n), rd[u]++;
		int l = 0, r = 0;
		que[r++] = {n + 1};
		while(l != r){
			int u = que[l];
			l = (l + 1) % N;
			for(int i = head[u]; i; i = e[i].nxt){
				int v = e[i].to;
				rd[v - n]--;
				f[v - n][0] = f[v - n][0] + min(f[u - n][0], f[u - n][1]);
				f[v - n][1]++;
				if(!rd[v - n])
					que[r] = v, r = (r + 1) % N;
			}
		}
		if(min(f[n][0], f[n][1]) > k && min(f[n][0], f[n][1]) > n - k){
			puts("impossible");
			return 0;
		}
		int tmp = min(f[n][0], f[n][1]);
		if(tmp > k){
			k = n - k;
			swap(ans1, ans2);
		}
		print(n * 3);
		for(int i = 1; i <= n; i++){
			if(tmp < k && ans[i] == ans2)
				ans[i] = ans1, tmp++;
			putchar(ans[i] ? 'N' : 'S');
		}
		return 0;
	}
}
int main(){
	return LZZMD::main();
}
//14MB