import std.stdio, std.array, std.string, std.conv, std.algorithm;
import std.typecons, std.range, std.random, std.math, std.container;
import std.numeric, std.bigint, core.bitop, core.stdc.string, core.stdc.stdlib;

void main() {
    auto N = readln.chomp.to!int;
    auto S = readln.chomp.map!(c => c.to!int).array;

    S.uniq.array.length.writeln;
}
