// Slower C++ solution:
#include <bits/stdc++.h>

#define INF 1e9

using namespace std;



vector<vector<int> > A;

void Min(int &a,int b){a=min(a,b);}



bool DP(){

  sort(A.begin(),A.end());

  A.erase(unique(A.begin(),A.end()),A.end());

    

  int n = A.size();

  for(int i=0;i<n;i++)

    for(int j=0,used[10]={};j<A[i].size();j++)if(used[A[i][j]]++) return 1;





  vector<vector<int> >dp(1<<10,vector<int>(1<<10,INF));

  dp[0][0] = 0;



  for(int i=0;i<n;i++){

    for(int j=(1<<10)-1;j>=0;j--)

      for(int k=(1<<10)-1;k>=0;k--){

	if(dp[j][k] == INF||dp[j][k] == 10) continue;

	if((j&&k)&&__builtin_popcount(j&k) == dp[j][k]) return 1;



	for(int l=0,nj=j;l<(int)A[i].size();l++){

	  int num = A[i][l];

	  if(l)Min(dp[nj][k|(1<<num)],dp[j][k]+1);

	  if(j&(1<<num))break;

	  nj |= (1<<num);

	  Min(dp[nj][k],dp[j][k]+1);

	}

      }

  }

  



  for(int i=1;i<(1<<10);i++)

    for(int j=1;j<(1<<10);j++){

      if(__builtin_popcount(i&j) == dp[i][j]) return 1;

    }



  return 0;

}





typedef pair<int,int> P;

bool bfs(){

  sort(A.begin(),A.end());

  A.erase(unique(A.begin(),A.end()),A.end());

    

  int n = A.size();

  for(int i=0;i<n;i++)

    for(int j=0,used[10]={};j<A[i].size();j++)if(used[A[i][j]]++) return 1;

  

  queue<P> Q;

  vector<vector<int> >D(1<<10,vector<int>(1<<10,INF));

  D[0][0] = 0;

  Q.push(P(0,0));



  while(!Q.empty()){

    P t = Q.front();Q.pop();

    int I = t.first,J = t.second;

    if(I&&J&&__builtin_popcount(I&J) == D[I][J]) return 1;

    if(D[I][J]==10) continue;    



    for(int i=0;i<n;i++){

      for(int l=0,ni=I;l<(int)A[i].size();l++){

	int num = A[i][l];

	if(l&&D[ni][J|(1<<num)]==INF){

	  D[ni][J|(1<<num)] = D[I][J]+1;

	  Q.push(P(ni,J|(1<<num)));

	} 

	if(I&(1<<num))break;

	ni |= (1<<num);

	if(D[ni][J]==INF)D[ni][J] = D[I][J] + 1,Q.push(P(ni,J));

      }

    }

  }

  return 0;

}



int main(){

  int n;

  while(cin>>n,n){

    string str;

    cin>>str;

    A.clear();

    for(int i=0;i<str.size();i++){

      A.push_back(vector<int>());

      while(str[i]!='u') A.back().push_back(str[i++]-'0');

    }

    cout<<(bfs()? "UN":"")<<"SAFE"<<endl;

  }

  return 0;

}

// Faster C++ solution for the same problem (measured speedup: 3.8990779702392104x):
#include <bits/stdc++.h>

#define INF 1e9

using namespace std;

vector<vector<int> > A;

typedef pair<short,short> P;



bool bfs(){

  sort(A.begin(),A.end());

  A.erase(unique(A.begin(),A.end()),A.end());

  int n = A.size();

  for(int i=0;i<n;i++)

    for(int j=0,used[10]={};j<A[i].size();j++)if(used[A[i][j]]++) return 1;

  

  queue<P> Q;

  bool D[1<<10][1<<10]={};

  D[0][0]=1;

  Q.push(P(0,0));



  while(!Q.empty()){

    P t = Q.front();Q.pop();

    int I = t.first,J = t.second;

    if(I&&J&&__builtin_popcount(I&J) == __builtin_popcount(J)) return 1;



    for(int i=0;i<n;i++){

      for(int k=0,ni=I;k<A[i].size();k++){

	int num = A[i][k],nj =(J|1<<num);

	if(k&&D[ni][nj]==0&&J!=nj)D[ni][nj]=1, Q.push(P(ni,nj));

	if(I&(1<<num))break;

	ni |= (1<<num);

      }

    }

  }

  return 0;

}



int main(){

  int n;

  while(cin>>n,n){

    string str;

    cin>>str;

    A.clear();

    for(int i=0;i<str.size();i++){

      A.push_back(vector<int>());

      while(str[i]!='u') A.back().push_back(str[i++]-'0');

    }

    cout<<(bfs()? "UN":"")<<"SAFE"<<endl;

  }

  return 0;

}