{"raw_statement":[{"iden":"problem statement","content":"In a certain programming contest, T-shirts are awarded to participants according to the following rules.\n\n*   All participants who ranked $A$\\-th or higher get a T-shirt.\n*   Additionally, from the participants who ranked between $(A+1)$\\-th and $B$\\-th (inclusive), $C$ participants chosen uniformly at random get a T-shirt.\n\nThere were $1000$ participants in this contest, and all of them got different ranks.  \nIroha-chan, who participated in this contest, ranked $X$\\-th.  \nFind the probability that she gets a T-shirt."},{"iden":"constraints","content":"*   All values in input are integers.\n*   $1 \\le A < B \\le 1000$\n*   $1 \\le C \\le B-A$\n*   $1 \\le X \\le 1000$"},{"iden":"input","content":"Input is given from Standard Input in the following format:\n\n$A$ $B$ $C$ $X$"},{"iden":"sample input 1","content":"30 500 20 103"},{"iden":"sample output 1","content":"0.042553191489\n\nIroha-chan ranked $103$\\-rd.  \nShe will get a T-shirt if she is among the $20$ participants chosen uniformly at random from the $470$ participants who ranked between $31$\\-st and $500$\\-th, which happens with probability $\\frac{20}{470}=0.04255319\\dots$."},{"iden":"sample input 2","content":"50 500 100 1"},{"iden":"sample output 2","content":"1.000000000000\n\nIroha-chan ranked $1$\\-st. This time, she is guaranteed to get a T-shirt."},{"iden":"sample input 3","content":"1 2 1 1000"},{"iden":"sample output 3","content":"0.000000000000\n\nIroha-chan ranked $1000$\\-th. This time, she will never get a T-shirt."}],"translated_statement":null,"sample_group":[],"show_order":["default"],"formal_statement":null,"simple_statement":null,"has_page_source":true}