import std.algorithm;
import std.uni;
import std.array;
import std.file;
import std.stdio;

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

auto calculateTotalNumberOfQuestions(string input)
{
    return input.splitter("\n\n")
        .array.map!(group => group.filter!isAlpha.array.sort.uniq.count).sum;
}

unittest
{
    auto input = `abc

a
b
c

ab
ac

a
a
a
a

b`;

    assert(input.calculateTotalNumberOfQuestions == 11);
}