import std.stdio, std.conv, std.string, std.array, std.range, std.algorithm, std.container;
import std.math, std.random, std.bigint, std.datetime, std.format;
void main(string[] args){ if(args.length > 1) if(args[1] == "-debug") DEBUG = 1; solve(); }
void log()(){ writeln(""); } void log(T, A ...)(T t, lazy A a){ if(DEBUG) write(t, " "), log(a); } bool DEBUG = 0; 
string rstring(){ static string[] ss; while(!ss.length) ss = readln.chomp.split; string res = ss[0]; ss.popFront; return res; }
T rtype(T)(){ return rstring.to!T; } alias rint = rtype!int, rlong = rtype!long, rreal = rtype!real;
T[] rtypes(T)(int n){ return n.iota.map!(i => rtype!T()).array; } alias rint = rtypes!int, rlong = rtypes!long, rreal = rtypes!real;
T[][] rtypess(T)(int n, int m){ return n.iota.map!(i => rtypes!T(m)).array; } alias rint = rtypess!int, rlong = rtypess!long, rreal = rtypess!real;
T chmin(T)(ref T x, T y){ if(x > y) x = y; return x; } T chmax(T)(ref T x, T y){ if(x < y) x = y; return x; }

// ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- //

void solve(){
	int n = rint;
	int[] as = rint(n);

	Finite ans = Finite(1);
	int r, g, b;
	foreach(a; as){
		int x;
		if(r == a) x += 1;
		if(g == a) x += 1;
		if(b == a) x += 1;
		ans *= x;
		if(r == a) r += 1;
		else if(g == a) g += 1;
		else if(b == a) b += 1;
	}

	ans.writeln;
}
struct Finite{
	long value; static long mod = 1_000_000_007;
	private static long[] _inv = [0, 1], _frac = [1, 1], _invfrac = [1, 1];
	this(long v){ value = val(v); }
	static long val(long v){
		if(v >= 0) return v % mod;
		else return (v + mod  - (v / mod) * mod) % mod;
	}
	bool opCast(T: bool)(){ return value != 0; }
	Finite opUnary(string s){ long v;
		if(s == "+") v = value;
		else if(s == "-") v = mod - value;
		else if(s == "++") v = value + 1;
		else if(s == "--") v = value + mod - 1;
		else assert(0, "Operator unary " ~ s ~ " not implemented");
		return Finite(v);
	}
	Finite opBinary(string s)(Finite b){
		return opBinary!s(b.value);
	}
	Finite opBinary(string s)(long u){ long v;
		if(s == "+") v = value + u;
		else if(s == "-") v = value + mod - u;
		else if(s == "*") v = value * u;
		else if(s == "/") v = value * inv(u);
		else assert(0, "Operator " ~ s ~ " not implemented");
		return Finite(v);
	}
	Finite opBinaryRight(string s)(long u){ long v;
		if(s == "+") v = u + value;
		else if(s == "-") v = u + mod - value;
		else if(s == "*") v = u * value;
		else if(s == "/") v = u * invvalue;
		else assert(0, "Operator " ~ s ~ " not implemented");
		return Finite(v);
	}
	Finite opAssign(long v){ value = v; return this; }
	Finite opOpAssign(string s)(Finite b){
		return opOpAssign!s(b.value);
	}
	Finite opOpAssign(string s)(long v){
		if(s == "+") value = (value + v) % mod;
		else if(s == "-") value = (value + mod - v) % mod;
		else if(s == "*") value = (value * v) % mod;
		else if(s == "/") value = (value * inv(v)) % mod;
		else assert(0, "Operator " ~ s ~ "= not implemented");
		return this;
	}
	bool opEquals(Finite b){
		return(value == b.value);
	}
	string toString(){ return value.to!string; }
	long inv(long v){
		v = val(v);
		while(v >= _inv.length){
			_inv ~= _inv[mod % $] * (mod - mod / _inv.length) % mod;
		}
		return _inv[v];
	}
	long invvalue(){
		return inv(value);
	}
	static Finite opCall(long v){ return Finite(val(v)); }
	
}



Measured memory_bytes: 4440