#include <bits/stdc++.h>
using namespace std;
using namespace std::literals;
using Int = long long;
using Double = long double;
#define rep(i, n) for (int i = 0, i##_len = (int)(n); i < i##_len; i++)
#define reps(i, n) for (int i = 1, i##_len = (int)(n); i <= i##_len; i++)
#define ALL(v) (v).begin(), (v).end()
#define SZ(x) ((int)(x).size())
#define LEN(x) ((int)(x).length())
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end());
#define PUTS(x) cout << (x) << endl;
#define MP make_pair
#define MT make_tuple
#define PB push_back
#define F first
#define S second
#define perm(c)   \
    sort(ALL(c)); \
    for (bool c##p = 1; c##p; c##p = next_permutation(ALL(c)))
#define IntsIn(v, n)                                 \
    auto v = vector<Int>(0);                         \
    for (int v##_i = 0; v##_i < (int)(n); v##_i++) { \
        Int v##_a;                                   \
        cin >> v##_a;                                \
        v.push_back(v##_a);                          \
    }
void setPrecision(int num = 20) {
    std::cout << std::fixed << std::setprecision(num);
}
template <typename T>
T Max(T a) {
    return a;
}
template <typename T, typename... Args>
T Max(T a, Args... args) {
    return std::max(Max(args...), a);
}
template <typename T>
T Min(T a) {
    return a;
}
template <typename T, typename... Args>
T Min(T a, Args... args) {
    return std::min(Min(args...), a);
}
template <typename T>
bool vector_contains(std::vector<T> vec, T value) {
    return (std::distance(vec.begin(), std::find(vec.begin(), vec.end(), value)) != vec.size());
}
template <typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val) {
    std::fill((T *)array, (T *)(array + N), val);
}
template <typename... Args>
std::string format(const std::string &fmt, Args... args) {
    size_t len = std::snprintf(nullptr, 0, fmt.c_str(), args...);
    std::vector<char> buf(len + 1);
    std::snprintf(&buf[0], len + 1, fmt.c_str(), args...);
    return std::string(&buf[0], &buf[0] + len);
}
string toStringWithBase(Int value, int base) {
    auto r = value % base;
    auto q = value / base;
    auto s = (r < 10) ? ('0' + r) : ('A' + (r - 10));
    if (q == 0) {
        return format("%c", s);
    } else {
        return format("%s%c", toStringWithBase(q, base).c_str(), s);
    }
}
string toStringWithBase(Int value, int base, int padding) {
    auto result = toStringWithBase(value, base);
    auto n = result.size();
    auto Result = ""s;
    for (int i = n + 1; i <= padding; i++) {
        Result += "0"s;
    }
    return Result + result;
}
int main() {
    int n;
    cin >> n;
    auto v = vector<tuple<int, int, int>>(0);
    rep(i, n) {
        int a;
        cin >> a;
        rep(j, a) {
            int x, y;
            cin >> x >> y;
            x--;
            v.PB(MT(i, x, y));
        }
    }
    auto ans = 0;
    rep(i, 1LL << n) {
        auto bits = toStringWithBase(i, 2, n);
        auto success = true;
        for (auto data : v) {
            auto from = get<0>(data);
            auto about = get<1>(data);
            char info = '0' + get<2>(data);
            auto flag = (bits[from] == '1');
            auto bit = bits[about];
            if (flag && bit != info) {
                success = false;
                break;
            }
        }
        if (success) {
            auto a = i;
            auto b = 0;
            while (a > 0) {
                if ((a & 1) == 1) b++;
                a /= 2;
            }
            ans = max(ans, b);
        }
    }
    PUTS(ans);
}


Measured memory_bytes: 256