import core.bitop, std.algorithm, std.ascii, std.bigint, std.conv, std.math,
    std.functional, std.numeric, std.range, std.stdio, std.string, std.random,
    std.typecons, std.container, std.format;

// dfmt off
T lread(T = long)(){return readln.chomp.to!T();}
T[] aryread(T = long)(){return readln.split.to!(T[])();}
void scan(TList...)(ref TList Args){auto line = readln.split();
foreach (i, T; TList){T val = line[i].to!(T);Args[i] = val;}}
alias sread = () => readln.chomp();enum MOD = 10 ^^ 9 + 7;
alias PQueue(T, alias less = "a<b") = BinaryHeap!(Array!T, less);
// dfmt on

void main()
{
    long N = lread();
    auto honest = new ulong[](N);
    auto unkind = new ulong[](N);
    foreach (i; 0 .. N)
    {
        long A = lread();
        foreach (_; 0 .. A)
        {
            long x, y;
            scan(x, y);
            if (y)
            {
                honest[i] |= 1 << (x - 1);
            }
            else
            {
                unkind[i] |= 1 << (x - 1);
            }
        }
    }
    bool isValid(ulong mh)
    {
        foreach (i; 0 .. N)
            if ((mh & (1 << i)) != 0)
            {
                if ((unkind[i] & mh) != 0)
                    return false;
                if ((honest[i] & (~mh)) != 0)
                    return false;
            }
        return true;
    }

    long ans;
    foreach (mh; 0 .. (1 << N))
        if (isValid(mh))
        {
            ans = ans.max(popcnt(mh));
        }
    writeln(ans);
}
