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

string FMT_F = "%.10f";

static string[] s_rd;
T RD(T = long)() { while(!s_rd.length) s_rd = readln.chomp.split; string res = s_rd[0]; s_rd.popFront; return res.to!T; }
string RDR()() { return readln.chomp; }
T[] ARR(T = long)(in string str, T fix = 0) { auto r = str.split.to!(T[]); r[] += fix; return r; }
size_t[] MAKE_IDX(alias less = "a < b", Range)(Range range) { auto idx = new size_t[](range.length); makeIndex!(less)(range, idx); return idx;}
size_t MIN_POS(alias less = "a < b", Range)(Range range) { auto r = minPos!(less)(range); return range.length - r.length; }

bool inside(T)(T x, T b, T e) { return x >= b && x < e; }
bool minimize(T)(ref T x, T y) { if (x > y) { x = y; return true; } else { return false; } }
bool maximize(T)(ref T x, T y) { if (x < y) { x = y; return true; } else { return false; } }

long mod = 10^^9 + 7;
void moda(ref long x, long y) { x = (x + y) % mod; }
void mods(ref long x, long y) { x = ((x + mod) - (y % mod)) % mod; }
void modm(ref long x, long y) { x = (x * y) % mod; }


long[][] p_triangle(long n)
{
	auto dp = new long[][](n+1, n+1);
	dp[0][0] = 1;
	foreach (i; 1..n+1)
	{
		foreach (j; 0..n+1)
		{
			if (j >= 1)
				dp[i][j] = dp[i-1][j-1] + dp[i-1][j];
			else
				dp[i][j] = dp[i-1][j];
		}
	}
	return dp;
}

void main()
{
	auto N = RD;
	auto S = RD!string;

	auto pt = p_triangle(30);
	long[30] comb;
	foreach (i; 0..30)
	{
		foreach (e; pt[i][1..$])
			moda(comb[i], e);
	}
	//stderr.writeln(comb);
	long[30] cnt;
	long used;
	long ans;
	foreach (i, c; S)
	{
		auto num = c - 'a';
		if (cnt[num] > 0)
		{
			long x = comb[used-1];
			//stderr.writeln("x:", x, " used:", used);
			auto y = (i - cnt[num]);
			auto z = used - 1;
			long v ;
			foreach (i; 1..z+1) v += comb[y][i];
			modm(x, v);
			moda(x, 1);
			moda(ans, x);
		}
		else
		{
			modm(ans, 2);
			moda(ans, 1);
		}
		++cnt[num];
		if (cnt[num] == 1) ++used;
		//stderr.writeln(ans);
	}
	writeln(ans);
	stdout.flush();
}