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#include <iostream>
#include <vector>

#define MOD_VAL 1000000007
//#define DEBUG

uint64_t solve(int drzewa_left, int gatunki_left, int gatunki, std::vector<int> &day_len, int drzewa){
	uint64_t output;
	#ifdef DEBUG
	//std::cout << "solve " << drzewa_left << " " << gatunki_left << "\n";
	#endif
	if(drzewa_left == 0){ //Podzielone
		output=1;
		for(int i=0; i<day_len.size(); i++){
			#ifdef DEBUG
			std::cout << day_len[i] << " ";
			#endif
			output=(output*(gatunki-i))%MOD_VAL;
			for(uint64_t j=0; j<(day_len[i]-2); j++){
				output=(output*gatunki)%MOD_VAL;
			}
		}
		#ifdef DEBUG
		std::cout << "\n";
		std::cout << "output1: " << output << "\n";
		#endif
		//for(int i=1; i<=(drzewa-day_len.size()*2); i++){
		//	output=(output*gatunki)%MOD_VAL;
		//}
		//std::cout << "\n";
		#ifdef DEBUG
		std::cout << "adding: " << output << "\n";
		#endif
		return output;
	}
	if(gatunki_left == 0) return 0;
	output=0;
	for(int i=2; i<=drzewa_left; i++){
		day_len.push_back(i);
		output = (output+solve(drzewa_left-i, gatunki_left-1, gatunki, day_len, drzewa))%MOD_VAL;
		day_len.pop_back();
	}
	return output;
}

//int output;

int main(){
	std::ios_base::sync_with_stdio(false);
	std::cin.tie(NULL);

	int n,m;
	std::cin >> n >> m;
	//output=0;
	std::vector<int> day_len;
	uint64_t out = solve(n,m, m, day_len, n);
	//std::cout << "output:\n";
	std::cout << out << "\n";
}