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October 21, 2021 14:38
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aoj1604.cpp
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#include <bits/stdc++.h> | |
//#include <atcoder/all> | |
//using namespace atcoder; | |
#pragma GCC target ("avx2") | |
#pragma GCC optimization ("O3") | |
#pragma GCC optimization ("unroll-loops") | |
using namespace std; | |
typedef vector<int> VI; | |
typedef vector<VI> VVI; | |
typedef vector<string> VS; | |
typedef pair<int, int> PII; | |
typedef pair<int, int> pii; | |
typedef pair<long long, long long> PLL; | |
typedef pair<int, PII> TIII; | |
typedef long long ll; | |
typedef long double ld; | |
typedef unsigned long long ull; | |
#define FOR(i, s, n) for (int i = s; i < (int)n; ++i) | |
#define REP(i, n) FOR(i, 0, n) | |
#define rep(i, a, b) for (int i = a; i < (b); ++i) | |
#define trav(a, x) for (auto &a : x) | |
#define all(x) x.begin(), x.end() | |
#define MOD 1000000007 | |
template<class T1, class T2> inline bool chmax(T1 &a, T2 b) {if (a < b) {a = b; return true;} return false;} | |
template<class T1, class T2> inline bool chmin(T1 &a, T2 b) {if (a > b) {a = b; return true;} return false;} | |
const double EPS = 1e-8, PI = acos(-1); | |
const double pi = 3.141592653589793238462643383279; | |
bool dp[10][10][(1<<10)]; | |
int main() { | |
cin.tie(0); | |
ios::sync_with_stdio(false); | |
cout << fixed << setprecision(12); | |
int n; | |
while(cin >> n, n) { | |
string s; cin >> s; | |
bool ok = true; | |
REP(i,10) REP(j,10) REP(k,(1<<10)) dp[i][j][k] = false; | |
REP(i,10) dp[i][i][(1<<i)] = true; | |
REP(i,n) { | |
if(!ok) break; | |
int j = i; | |
while(j<n && s[j] != 'u') j++; | |
int mask = 0; | |
for(int k=i; k<j-1; k++) { | |
if(!ok) break; | |
int u = s[k]-'0', v = s[k+1]-'0'; | |
for(int l=0; l<10; l++) { | |
for(int bit=0; bit<(1<<10); bit++) { | |
if((mask & bit) != 0) continue; | |
dp[l][v][bit | mask | (1<<v)] |= dp[l][u][bit]; | |
if(l == v && dp[l][u][bit]) ok = false; | |
} | |
} | |
if(mask >> u & 1) ok = false; | |
mask |= (1<<u); | |
} | |
i = j; | |
} | |
cout << (ok?"SAFE":"UNSAFE") << '\n'; | |
} | |
return 0; | |
} |
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