T = int(input())
solution = []
for i in range (T):
t = input()
t = t.split(" ")
##print(t[0])
##print(type(t[0]))
##print(len(t))
rows = []
columns = []
R = int(t[0])
C = int(t[1])
counter = 0
for j in range®:
rows = []
x = input()
x = x.split(" ")
for l in x:
rows.append(int(l))
columns.append(rows)
for i in range(1,C-1):
for k in range(1,R-1):
if (columns[i][k]>columns[i][k-1] and columns[i][k]>columns[i][k+1] and columns[i][k]>columns[i-1][k] and columns[i][k]>columns[i+1][k]):
counter+= 4
else:
continue
if (counter == (R-1)*(C-1)):
solution.append("Stable")
else:
solution.append("Unstable")
##print(counter)
for i in solution:
print(i)
##print(solution)