e.cpp

//#define __GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;

#define REP(i, n) for(int i = 0; i < (int)(n); ++i)
#define pb push_back
#define ALL(a) (a.begin()), (a.end())
#define mp make_pair
#define F first
#define S second
#define SZ(a) ((int)(a.size()))

typedef long long ll;
typedef pair<int, int> PI;

int main(int argc, char *argv[])
{

  int n;
  while (cin >> n && n){
    string S;
    cin >> S;
    int dp[11][11][1 << 10];
    memset(dp, 0, sizeof(dp));
    bool unsafe = false;

    REP(i, n) if (i == 0 || S[i - 1] == 'u'){
      int s = i;
      if (S[s] == 'u' || S[s + 1] == 'u') continue;
      // cout << s << endl;

      int mask = 0;
      while (S[s] != 'u'){
        if (mask & (1 << (S[s] - '0'))){
          unsafe = true;
        } else {
          // cout << s << " " << S[s] << " " << mask << endl;
          dp[0][S[s] - '0'][mask] = 1;
        }
        mask |= 1 << (S[s] - '0');
        s++;
      }
    }


    REP(t, 10) if (t > 0){
      REP(d, 10) REP(mask, 1 << 10) if (dp[t - 1][d][mask]){
        REP(i, n - 1) if (S[i] == 'u' && S[i + 1] != 'u'){
          int n_mask = 0;
          int p = i + 1;
          while (S[p] != 'u' && (mask & (1 << (S[p] - '0'))) == 0){
            n_mask |= 1 << (S[p] - '0');
            p++;
          }
          // cout << t << " " << d << " " << mask << " " << p << " " << n_mask << endl;

          if (S[p] != 'u'){
            if ((n_mask  | mask) & (1 << d)) unsafe = true;
            dp[t][d][mask | n_mask] = 1;
          }
        }
      }
    }
    if (unsafe) {
      cout << "UNSAFE" << endl;
    } else {
      cout << "SAFE" << endl;
    }
  }
  return 0;
}