def solve(n, m, x, portals):
    T = n * n
    portal_map = {st: ed for st, ed in portals}
    
    visited = set()
    pos = 1
    while True:
        if pos == T:
            return "yes"
        if pos in visited:
            return "no"
        visited.add(pos)
        
        if pos + x <= T:
            next_pos = pos + x
        else:
            return "yes" if (T - pos) % x == 0 else "no"
        
        while next_pos in portal_map:
            next_pos = portal_map[next_pos]
            
        pos = next_pos
n,m,x=map(int,input().split())
    
portals = []
for _ in range(m):
    st,ed =map(int,input().split())
    portals.append((st,ed))
    
print(solve(n, m, x, portals))

第一次超过T（理论上要折返继续操作）但直接输出no就可过