#include<bits/stdc++.h>
using namespace std;
int n,m,k,a[1<<20],x,y;
vector<int>e[1<<20];
queue<int>q;
int main(){
	cin>>n>>m>>k,a[1]=1,a[n]=2,q.push(1);
	for(int i=1;i<=n;i++)
		cin>>x;
	for(int i=1;i<=m;i++){
		cin>>x>>y,e[x].push_back(y),e[y].push_back(x);
		if(x==1&&y==n||x==n&&y==1){
			if(n==2&&k==1)
				cout<<"impossible\n",exit(0);
			if(k>1)
				cout<<string(k-1,'N')<<string(n-k,'S')<<"N\n",exit(0);
			cout<<string(k-1,'S')<<string(n-k,'N')<<"S\n",exit(0);
		}
	}
	if(!k)
		cout<<string(n,'S')<<'\n',exit(0);
	while(q.size()&&k>1){
		x=q.front(),q.pop();
		for(int y:e[x])
			if(!a[y])
				a[y]=1,q.push(y),k--;
	}
	for(int i=1;i<=n;i++)
		cout<<(a[i]==1?'N':'S');
	cout<<'\n';
}