{"problem":{"name":"Iroha and a Grid","description":{"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","description_type":"Markdown"},"platform":"AtCoder","limit":{"time_limit":2000,"memory_limit":262144},"difficulty":"None","is_remote":true,"is_sync":true,"sync_url":null,"sign":"arc058_b"},"statements":[{"statement_type":"Markdown","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 $10^9+7$.\n\n## Constraints\n\n*   $1 ≦ H, W ≦ 100,000$\n*   $1 ≦ A < H$\n*   $1 ≦ B < W$\n\n## Input\n\nThe input is given from Standard Input in the following format:\n\n$H$ $W$ $A$ $B$\n\n[samples]","is_translate":false,"language":"English"}],"meta":{"iden":"arc058_b","tags":[],"sample_group":[["2 3 1 1","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\"."],["10 7 3 4","3570\n\nThere are $12$ forbidden cells."],["100000 100000 99999 99999","1"],["100000 100000 44444 55555","738162020"]],"created_at":"2026-03-03 11:01:13"}}