n=int(input().strip()) sums=0 res='YES' for i in range(n): a=list(map(int,input().split())) for j in range(len(a)): if i>0 and j<i and a[j]!=0: res='NO' print(res)
n=int(input().strip()) sums=0 res='YES' for i in range(n): a=list(map(int,input().split())) for j in range(len(a)): if i>0 and j<i and a[j]!=0: res='NO' print(res)