#include <bits/stdc++.h>

using namespace std;

#define REP(i, n) for (int i=0; i<(n); ++i)
#define RREP(i, n) for (int i=(int)(n)-1; i>=0; --i)
#define FOR(i, a, n) for (int i=(a); i<(n); ++i)
#define RFOR(i, a, n) for (int i=(int)(n)-1; i>=(a); --i)

#define SZ(x) ((int)(x).size())
#define all(x) begin(x),end(x)

#define dump(x) cerr<<#x<<" = "<<(x)<<endl
#define debug(x) cerr<<#x<<" = "<<(x)<<" (L"<<__LINE__<<")"<<endl;

template<class T>
ostream &operator<<(ostream &os, const vector <T> &v) {
    os << "[";
    REP(i, SZ(v)) {
        if (i) os << ", ";
        os << v[i];
    }
    return os << "]";
}

template<class T, class U>
ostream &operator<<(ostream &os, const pair <T, U> &p) {
    return os << "(" << p.first << " " << p.second << ")";
}

template<class T>
bool chmax(T &a, const T &b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

template<class T>
bool chmin(T &a, const T &b) {
    if (b < a) {
        a = b;
        return true;
    }
    return false;
}

using ll = long long;
using ull = unsigned long long;
using ld = long double;
using P = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;
using vvi = vector<vi>;
using vvll = vector<vll>;

const ll MOD = 1e9 + 7;
const int INF = INT_MAX / 2;
const ll LINF = LLONG_MAX / 2;
const ld EPS = 1e-9;

using State = string::const_iterator;
struct OutOfRangeError {};
struct UnAssignedError {};

map<char,map<int,int>> env;
map<char,int> env_len;

int number(State &begin) {
    int ret = 0;
    while ('0' <= *begin and *begin <= '9') {
        ret *= 10;
        ret += *begin - '0';
        ++begin;
    }
    return ret;
}

int expression(State &begin) {
    if ('0' <= *begin and *begin <= '9') {
        return number(begin);
    }
    char array_name = *begin;
    ++begin;
    ++begin; // [
    int idx = expression(begin);
    ++begin; // ]
    if (env_len[array_name] <= idx) throw OutOfRangeError();
    if (env[array_name].count(idx) == 0) throw UnAssignedError();
    return env[array_name][idx];
}

void statement(State &begin) {
    char array_name = *begin;
    ++begin;
    ++begin; // [
    int num = expression(begin);
    ++begin; // ]
    if (*begin == 0) {
        env_len[array_name] = num;
    } else if (*begin == '=') {
        if (env_len[array_name] <= num) throw OutOfRangeError();
        ++begin; // =
        int exp = expression(begin);
        env[array_name][num] = exp;
    }
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);

    for (;;) {
        env.clear();
        env_len.clear();
        vector<string> ss;
        for (;;) {
            string s; cin >> s;
            if (s == ".") break;
            ss.push_back(s);
        }
        if (ss.size() == 0) break;

        int ans = 0;
        REP(i, SZ(ss)) {
            State begin = ss[i].begin();
            try {
                statement(begin);
            } catch (OutOfRangeError &e) {
                ans = i+1;
                break;
            } catch (UnAssignedError &e) {
                ans = i+1;
                break;
            }
        }
        cout << ans << endl;
    }

    return 0;
}



Measured memory_bytes: 3328