a, b= 1, 2
for i in range(3,n+1):
    a, b  = b, a + b
return b

a, b, c = 1, 2, 4 
for i in range(4, n+1):
    a, b, c = b, c, a + b + c
return c

3
7 5 4 5 8
7 5 4 5 2
20 53 45 26 4

2 1
-1
1 3

t = int(input())
for _ in range(t):
    a, b, c, d, k = map(int, input().split())
    pens_needed = (a + c - 1) // c  # Ceiling of a/c
    pencils_needed = (b + d - 1) // d  # Ceiling of b/d
    if pens_needed + pencils_needed <= k:
        print(pens_needed, pencils_needed)
    else:
        print(-1)

x = q - p / 2,   y = q + p / 2

Answer = (even_P × even_Q) + (odd_P × odd_Q)

for _ in range(int(input())):
    n, P = int(input()), list(map(int, input().split()))
    m, Q = int(input()), list(map(int, input().split()))
    
    eP = sum(p % 2 == 0 for p in P)  # Count evens in P
    oP = n - eP                      # Count odds in P
    eQ = sum(q % 2 == 0 for q in Q)  # Count evens in Q
    oQ = m - eQ                      # Count odds in Q
    
    print(eP * eQ + oP * oQ)

3
3
1 3 2
2
0 3
1
1
1
1
1
2
1
1

3
1
0

3

2 8 5
9 3 4
7 6 1

def main():
    n = int(input())
    groups = [[] for _ in range(n)]
    num = 1

    for row in range(n):
        # decide direction: left‑to‑right on even rows, right‑to‑left on odd
        cols = range(n) if row % 2 == 0 else range(n - 1, -1, -1)
        for col in cols:
            groups[col].append(num)
            num += 1

    # output
    for g in groups:
        print(*g)

if __name__ == "__main__":
    main()

2
1 2

YES

def main():
    def iinp(): return (int(input()))
    def linp(): return (list(map(int, input().split())))
    n = iinp()
    arr = [0 for i in range(n+1)]
    for i in range(n-1):
            u,v = linp()
            arr[u] += 1
            arr[v] += 1
    for i in arr:
        if i ==2:
            print("NO")
            return 
    print("YES")
main()