PROGRAMMING:The other side of ZF series

Through the fog filled forest, ZF seems to see MM is waving to him, smile, the test of the devil will not end like this~~~~
In front of ZF is a magmatic river. Fortunately, ZF has learned the art of Royal sword. Suddenly, a roar comes from behind. Under the pursuit of Huo Qilin, can ZF reach the other side safely?
Input n is the sword speed of ZF, M is the pursuit speed of huoqilin, the cliff width is L1 meters, and the distance between huoqilin and ZF is L2 meters
If you can reach the other side, output yes, otherwise output No
###Input format:
Input n is the sword speed of ZF, M is the pursuit speed of huoqilin, the cliff width is L1 meters, and the distance between huoqilin and ZF is L2 meters
###Output format:
If you can reach the other side, output yes, otherwise output No
###Input example:
Here is a set of inputs. For example:
```in
67 48 3225 4134
```
###Output example:
The corresponding output is given here. For example:
```out
yes
```
Tips
This group of test data input to the end of the file remember to use= EOF






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