#include <bits/stdc++.h>
#define pb push_back
#define all(x) x.begin(), x.end()

using namespace std;
using vi = vector<int>;

const int N = 1e6;
vi adj[N], topsort;
bool vis[N];
int ind[N], dp[N], n;

void dfs(int node) {
    for(const int& v:adj[node]) {
        dfs(v);
    }
    topsort.pb(node);
    return;
}

bool verify() {
    reverse(all(topsort));
    for(int i = 0;i<n;++i) {
        ind[topsort.at(i)] = i;
    }
    for(int i = 0;i<n;++i) {
        for(const int& v:adj[i]) {
            if (ind[v] <= ind[i]) {
                return false;
            }
        }
    }
    return true;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    memset(vis, false, sizeof vis);
    string s;
    cin >> s;
    n = s.length();
    for(int i = 0;i<n - 1;++i) {
        adj[i].pb(i + 1);
    }
    dfs(0);
    if (verify()) {
        memset(dp, 0, sizeof dp);
        dp[topsort.at(0)] = (s[topsort.at(0)] == 'Z' || s[topsort.at(0)] == 'z');
        for(const int& v:topsort) {
            for(const int& u:adj[v]) {
                dp[u] = max(dp[u], dp[v] + (s[u] == 'Z' || s[u] == 'z'));
            }
        }
        cout << (dp[n - 1] == 0 ? "NO":to_string(dp[n - 1])) << endl;
    }
    else {
        cout << "ERROR" << endl;
    }
    return 0;
}