#define  _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES

#pragma comment (linker, "/STACK:526000000")

#include "bits/stdc++.h"
#define int ll

using namespace std;
typedef string::const_iterator State;
#define eps 1e-8L
#define MAX_MOD 1000000007LL
#define GYAKU 500000004LL
#define MOD 998244353LL
#define pb push_back
#define mp make_pair
typedef long long ll;
typedef long double ld;
#define REP(a,b) for(long long (a) = 0;(a) < (b);++(a))
#define ALL(x) (x).begin(),(x).end()
//Do not use library.

template< typename flow_t, typename cost_t >
struct PrimalDual {
    const cost_t INF;

    struct edge {
        int to;
        flow_t cap;
        cost_t cost;
        int rev;
        bool isrev;
    };
    vector< vector< edge > > graph;
    vector< cost_t > potential, min_cost;
    vector< int > prevv, preve;

    PrimalDual(int V) : graph(V), INF(numeric_limits< cost_t >::max()) {}

    void add_edge(int from, int to, flow_t cap, cost_t cost) {
        graph[from].emplace_back(edge{ to, cap, cost, (int)graph[to].size(), false });
        graph[to].emplace_back(edge{ from, 0, -cost, (int)graph[from].size() - 1, true });
    }

    cost_t min_cost_flow(int s, int t, flow_t f) {
        int V = (int)graph.size();
        cost_t ret = 0;
        using Pi = pair< cost_t, int >;
        priority_queue< Pi, vector< Pi >, greater< Pi > > que;
        potential.assign(V, 0);
        preve.assign(V, -1);
        prevv.assign(V, -1);

        while (f > 0) {
            min_cost.assign(V, INF);
            que.emplace(0, s);
            min_cost[s] = 0;
            while (!que.empty()) {
                Pi p = que.top();
                que.pop();
                if (min_cost[p.second] < p.first) continue;
                for (int i = 0; i < graph[p.second].size(); i++) {
                    edge& e = graph[p.second][i];
                    cost_t nextCost = min_cost[p.second] + e.cost + potential[p.second] - potential[e.to];
                    if (e.cap > 0 && min_cost[e.to] > nextCost) {
                        min_cost[e.to] = nextCost;
                        prevv[e.to] = p.second, preve[e.to] = i;
                        que.emplace(min_cost[e.to], e.to);
                    }
                }
            }
            if (min_cost[t] == INF) return -1;
            for (int v = 0; v < V; v++) potential[v] += min_cost[v];
            flow_t addflow = f;
            for (int v = t; v != s; v = prevv[v]) {
                addflow = min(addflow, graph[prevv[v]][preve[v]].cap);
            }
            f -= addflow;
            ret += addflow * potential[t];
            for (int v = t; v != s; v = prevv[v]) {
                edge& e = graph[prevv[v]][preve[v]];
                e.cap -= addflow;
                graph[v][e.rev].cap += addflow;
            }
        }
        return ret;
    }

    void output() {
        for (int i = 0; i < graph.size(); i++) {
            for (auto& e : graph[i]) {
                if (e.isrev) continue;
                auto& rev_e = graph[e.to][e.rev];
                cout << i << "->" << e.to << " (flow: " << rev_e.cap << "/" << rev_e.cap + e.cap << ")" << endl;
            }
        }
    }
};

void solve() {
    int a;
    cin >> a;
    if (a % 9 == 0) {
        cout << 9 << endl;
    }else
    cout << a % 9 << endl;
}
#undef int
int main() {
    solve();
}