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#include<bits/stdc++.h>
//#include<unordered_set>
// #pragma GCC optimize("Ofast")
using namespace std;
#define int long long
#define die(x) return cout << x << endl, 0
#define FI first
#define SE second
#define all(o) o.begin(), o.end()
#define endl '\n'
#define IOS ios::sync_with_stdio(0), cin.tie(0)
#define FILE freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout)
#define SZ(x) ((int)(x).size())
#define PB push_back
#define PF push_front
#define POB pop_back
#define POF pop_front
#define MP make_pair
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef map<int,int> mpi;
typedef set<int> sti;
typedef vector<pii> vii;
typedef map<pii,int> mpii;
typedef set<pii> stii;
typedef long double ld;
typedef long long ll;
int gcd(int x,int y){ return (!y ? x : gcd(y, x%y)); }
int power(int x, int y) { return (!y ? 1 : power(x, y / 2) * power(x, y / 2) * (y % 2 ? x : 1)); }
int to_int(string sconvert){stringstream geek(sconvert);int xconvert = 0; geek >> xconvert; return xconvert;}
int fastMax(int x, int y) { return (((y-x)>>(32-1))&(x^y))^y; }
int fastMin(int x, int y) { return (((y-x)>>(32-1))&(x^y))^x; }
const int MAXN=2e5+30,MAX_LOG=30,MOD=1e9+7,INF=1e17;
const double PI = acos(-1);
int mod(int x) { return (x % MOD + MOD) % MOD; }
int n, m, q;

int d[MAXN];
vi g[MAXN];
int p[MAXN];
int state[MAXN];
bool has_cycle;
// void dijkstra(int source) {
//     fill(d,d+MAXN,INF);
//     priority_queue<pii, vector<pii>, greater<pii> > Q; 
//     d[source] = 0;
//     Q.push(make_pair(0,source));
//     while(!Q.empty()){
//         int current_distance = Q.top().first;
//         int u = Q.top().second;
//         Q.pop();
//         if(current_distance != d[u]) continue;
//         for(int i=0;i<g[u].size() ; i++){
//             pair<int,int> c=g[u][i];
//             int v = c.first;
//             int w = c.second;
//             if(d[v] > d[u]+w){
//                 d[v] = d[u]+w;
//                 p[v]=u;
//                 Q.push(make_pair(d[v],v));
//             }
//         }
//     }
// }

vi order;

void dfs(int u) {
    state[u] = 1;

    for (int v : g[u]) {
        if(state[v] == 0){
            dfs(v);
        }
        else if(state[v] == 1){
            has_cycle = true;
        }
    }

    state[u] = 2;
    order.push_back(u);
}

int MAIN(){
    cin>>n>>m;
    for(int i=0;i<m;i++){
        int a,b;
        cin>>a>>b;
        g[a].PB(b);
    }

    for(int i=1;i<=n;i++){
        if(state[i] == 0){
            dfs(i);
        }
    }

    if(has_cycle){
        cout<<"IMPOSSIBLE"<<endl;
        return 0;
    }

    reverse(order.begin(), order.end());
    for(int i=0;i<n;i++){
        cout<<order[i]<<" ";
    }
    
    return 0;
}

int32_t main(){
    IOS;
    int t=1;
    //cin>>t;
    while(t--)MAIN();
    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED