Swapping letters

l0 = {}
f = {}

for c in 'abcdefghijklmnopqrstuvwxyz':
    l0[c] = []
    f[c] = 1

def find(y, c, m):
    i = 0
    while True:
        if y[i] is c:
            m -= 1
            if m <= 0:
                return i
        i += 1

def main():
    n = int(input())
    
    while n > 0:
        n -= 1
        cs = input()
        c0 = cs[0]
        c1 = cs[2]
        l0[c0] += c1
        l0[c1] += c0
    
    
    
    x = input()
    y = input()

    if sorted(x) != sorted(y):
        print("NO")
        return

    i = 0
    while i < len(x):
        c = x[i]

        j = find(y, c, f[c])

        for r in l0[c]:
            if x[0:i].count(r) != x[0:j].count(r):
                #print(r)
                #print(i, j)
                print("NO")
                return
        f[c] += 1
        i += 1

    print("YES")

main()

Test 1

Verdict: WRONG ANSWER

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: WRONG ANSWER

Test 5

Verdict: ACCEPTED

Test 6

Verdict: TIME LIMIT EXCEEDED

Test 7

Verdict: TIME LIMIT EXCEEDED

Test 8

Verdict: TIME LIMIT EXCEEDED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED