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

enum inf = 1_001_001_001;
enum inf6 = 1_001_001_001_001_001_001L;
enum mod = 1_000_000_007L;

alias Pair = Tuple!(int, "a", int, "b");

void main() {
    int N;
    scan(N);
    auto s = readln.chomp.map!(ch => ch - '0').array;

    auto dp = new bool[][](1000, 4);
    dp[0][0] = 1;

    foreach (i ; 0 .. N) {
        foreach_reverse (k ; 0 .. 4) {
            foreach (j ; 0 .. 1000) {
                if (dp[j][k] && k < 3) {
                    dp[10*j + s[i]][k + 1] |= dp[j][k];
                }
            }
        }
    }

    int ans;

    foreach (j ; 0 .. 1000) {
        ans += dp[j][3];
    }

    writeln(ans);
}







void scan(T...)(ref T args) {
    import std.stdio : readln;
    import std.algorithm : splitter;
    import std.conv : to;
    import std.range.primitives;

    auto line = readln().splitter();
    foreach (ref arg; args) {
        arg = line.front.to!(typeof(arg));
        line.popFront();
    }
    assert(line.empty);
}

void fillAll(R, T)(ref R arr, T value) {
    static if (is(typeof(arr[] = value))) {
        arr[] = value;
    }
    else {
        foreach (ref e; arr) {
            fillAll(e, value);
        }
    }
}

bool chmin(T, U...)(ref T x, U args) {
    bool isChanged;

    foreach (arg; args) {
        if (x > arg) {
            x = arg;
            isChanged = true;
        }
    }

    return isChanged;
}

bool chmax(T, U...)(ref T x, U args) {
    bool isChanged;

    foreach (arg; args) {
        if (x < arg) {
            x = arg;
            isChanged = true;
        }
    }

    return isChanged;
}
