{"raw_statement":[{"iden":"problem statement","content":"We have a large square grid with $H$ rows and $W$ columns. Iroha is now standing in the top-left cell. She will repeat going right or down to the adjacent cell, until she reaches the bottom-right cell.\nHowever, she cannot enter the cells in the intersection of the bottom $A$ rows and the leftmost $B$ columns. (That is, there are $A×B$ forbidden cells.) There is no restriction on entering the other cells.\nFind the number of ways she can travel to the bottom-right cell.\nSince this number can be extremely large, print the number modulo $10^9+7$."},{"iden":"constraints","content":"*   $1 ≦ H, W ≦ 100,000$\n*   $1 ≦ A < H$\n*   $1 ≦ B < W$"},{"iden":"input","content":"The input is given from Standard Input in the following format:\n\n$H$ $W$ $A$ $B$"},{"iden":"sample input 1","content":"2 3 1 1"},{"iden":"sample output 1","content":"2\n\nWe have a $2×3$ grid, but entering the bottom-left cell is forbidden. The number of ways to travel is two: \"Right, Right, Down\" and \"Right, Down, Right\"."},{"iden":"sample input 2","content":"10 7 3 4"},{"iden":"sample output 2","content":"3570\n\nThere are $12$ forbidden cells."},{"iden":"sample input 3","content":"100000 100000 99999 99999"},{"iden":"sample output 3","content":"1"},{"iden":"sample input 4","content":"100000 100000 44444 55555"},{"iden":"sample output 4","content":"738162020"}],"translated_statement":null,"sample_group":[],"show_order":["default"],"formal_statement":null,"simple_statement":null,"has_page_source":true}