public int uniquePaths(int m, int n) {
		if (n < 1 || m < 1)
			return 0;
		int[][] steps = new int[m][n];
		for (int i = 0; i < m; i++) {
			steps[i][0] = 1;
		}
		for (int j = 0; j < n; j++) {
			steps[0][j] = 1;
		}
		for (int i = 1; i < m; i++) {
			for (int j = 1; j < n; j++) {
				steps[i][j] = steps[i - 1][j] + steps[i][j - 1];
			}
		}
		return steps[m - 1][n - 1];
	}