def find_wire(m, q, games, wires): # Create a union-find set uf = UnionFind(m)

# Iterate through the wires
for wire in wires:
    # Connect the two friends and merge their groups
    uf.union(wire[0]-1, wire[1]-1)

    # Check if the group that the friends belong to now contains all the friends
    # in the same game
    game = games[wire[0]-1]
    if uf.find(game-1) == uf.find(game):
        print(wire[0])
        return

# If no group contains all the friends in the same game, print -1
print(-1)

Union-find set class

class UnionFind: def init(self, n): self.parent = [i for i in range(n)] self.size = [1] * n

def find(self, x):
    if self.parent[x] != x:
        self.parent[x] = self.find(self.parent[x])
    return self.parent[x]

def union(self, x, y):
    x_root = self.find(x)
    y_root = self.find(y)
    if x_root == y_root:
        return
    if self.size[x_root] < self.size[y_root]:
        self.parent[x_root] = y_root
        self.size[y_root] += self.size[x_root]
    else:
        self.parent[y_root] = x_root
        self.size[x_root] += self.size[y_root]

Read input

m, n, q = map(int, input().split()) games = list(map(int, input().split())) wires = [tuple(map(int, input().split())) for _ in range(q)]

Find the wire

find_wire(m, q, games, wires)