rod_temp.cpp

#include <iostream>
#include <cstdlib>
#include <stack>
#include <cstring>
#include <vector>
#include <algorithm>

using namespace std;

int main() {

    int n;
    cin >> n;

    vector<int> adj[n];

    for(int i = 0; i < n; i++) {
        int a, b;
        cin >> a >> b;

        a--, b--;

        adj[a].push_back(b);
    }

    bool consegue = true;

    for(int i = 0; i < n; i++) {
        int vis[n];
        memset(vis, 0, sizeof vis);

        stack<int> pilha;
        pilha.push(i);

        while(!pilha.empty()) {
            int v = pilha.top();
            vis[v] = 1;

            bool found = false;

            for(int i = 0; i < n; i++)
                if(find(adj[v].begin(), adj[v].end(), i) != adj[v].end() && v != i && vis[i] == 0) {
                    pilha.push(i);
                    vis[i] = 1;
                    found = true;
                }

            if(!found)
                pilha.pop();
        }

        for(int j = 0; j < n; j++)
            if(!vis[j]) {
                i = n + 1;
                consegue = false;
                break;
            }
    }

    cout << ((consegue) ? "S" : "N") << endl;

    return 0;
}