In some game by Playrix it takes *t* minutes for an oven to bake *k* carrot cakes, all cakes are ready at the same moment *t* minutes after they started baking. Arkady needs at least *n* cakes to complete a task, but he currently don't have any. However, he has infinitely many ingredients and one oven. Moreover, Arkady can build one more similar oven to make the process faster, it would take *d* minutes to build the oven. While the new oven is being built, only old one can bake cakes, after the new oven is built, both ovens bake simultaneously. Arkady can't build more than one oven.

Determine if it is reasonable to build the second oven, i.e. will it decrease the minimum time needed to get *n* cakes or not. If the time needed with the second oven is the same as with one oven, then it is unreasonable.
The only line contains four integers *n*, *t*, *k*, *d* (1 ≤ *n*, *t*, *k*, *d* ≤ 1 000) — the number of cakes needed, the time needed for one oven to bake *k* cakes, the number of cakes baked at the same time, the time needed to build the second oven.
In the first example it is possible to get 8 cakes in 12 minutes using one oven. The second oven can be built in 5 minutes, so after 6 minutes the first oven bakes 4 cakes, the second oven bakes 4 more ovens after 11 minutes. Thus, it is reasonable to build the second oven. 

In the second example it doesn't matter whether we build the second oven or not, thus it takes 12 minutes to bake 8 cakes in both cases. Thus, it is unreasonable to build the second oven.

In the third example the first oven bakes 11 cakes in 3 minutes, that is more than needed 10. It is unreasonable to build the second oven, because its building takes more time that baking the needed number of cakes using the only oven.
8 6 4 5
YES
8 6 4 6
NO
10 3 11 4
NO
4 2 1 4
YES
28 17 16 26
NO
60 69 9 438
NO
599 97 54 992
YES
11 22 18 17
NO
1 13 22 11
NO
1 1 1 1
NO
3 1 1 1
YES
1000 1000 1000 1000
NO
1000 1000 1 1
YES
1000 1000 1 400
YES
1000 1000 1 1000
YES
1000 1000 1 999
YES
53 11 3 166
YES
313 2 3 385
NO
214 9 9 412
NO
349 9 5 268
YES
611 16 8 153
YES
877 13 3 191
YES
340 9 9 10
YES
31 8 2 205
NO
519 3 2 148
YES
882 2 21 219
NO
982 13 5 198
YES
428 13 6 272
YES
436 16 14 26
YES
628 10 9 386
YES
77 33 18 31
YES
527 36 4 8
YES
128 18 2 169
YES
904 4 2 288
YES
986 4 3 25
YES
134 8 22 162
NO
942 42 3 69
YES
894 4 9 4
YES
953 8 10 312
YES
43 8 1 121
YES
12 13 19 273
NO
204 45 10 871
YES
342 69 50 425
NO
982 93 99 875
NO
283 21 39 132
YES
1000 45 83 686
NO
246 69 36 432
NO
607 93 76 689
NO
503 21 24 435
NO
1000 45 65 989
NO
30 21 2 250
YES
1000 49 50 995
NO
383 69 95 253
YES
393 98 35 999
YES
1000 22 79 552
NO
268 294 268 154
NO
963 465 706 146
YES
304 635 304 257
NO
4 2 1 6
NO
1 51 10 50
NO
5 5 4 4
YES
3 2 1 1
YES
3 4 3 3
NO
7 3 4 1
YES
101 10 1 1000
NO
5 1 1 1
YES
5 10 5 5
NO
19 1 7 1
YES
763 572 745 262
YES
1 2 1 1
NO
5 1 1 3
YES
170 725 479 359
NO
6 2 1 7
YES
6 2 5 1
YES
1 2 2 1
NO
24 2 8 3
YES
7 3 3 3
YES
5 2 2 2
YES
3 2 1 2
YES
1000 2 200 8
NO
3 100 2 100
NO
2 999 1 1000
NO
2 1 1 1
NO
2 3 5 1
NO
100 1 5 1
YES
7 2 3 3
YES
4 1 1 3
NO
3 2 2 1
YES
1 1 1 2
NO
91 8 7 13
YES
3 1 2 1
NO
5 3 2 3
YES
9 6 6 3
YES
import math 
a = list(map(int,input().split()))

n = a[0]
t = a[1]
k = a[2]
d = a[3]

t1 = t*( (n/k) + (n%k!=0))
 
t2 = d + t*(( n-(d/t)*k )/(2*k) +(( n-(d/t)*k )%(2*k)!=0))
 
if(t2 < t1):
    print('YES')
else:
    print('NO')