import std.algorithm;
import std.uni;
import std.array;
import std.file;
import std.stdio;
import std.range;
import std.conv;
import std.string;

void main()
{
    readText("input").calculateTotalNumberOfQuestions.writeln;
}

auto setIntersectionRoR(RoR)(RoR ror)
{
    assert(!ror.empty);
    return ror.map!(to!(dchar[]))
        .reduce!((r1, r2) => r1.setIntersection(r2).array);
}

auto calculateTotalNumberOfQuestions(string input)
{
    return input.splitter("\n\n").array.map!((group) {
        return group.splitter.map!(person => person.representation.dup.sort.array.assumeUTF)
            .setIntersectionRoR.count;
    }).sum;
}

unittest
{
    auto input = `abc

a
b
c

ab
ac

a
a
a
a

b

yx`;

    assert(input.calculateTotalNumberOfQuestions == 8);
}