{"problem":{"name":"The Pilots Brothers' refrigerator","description":{"content":"The game “The Pilots Brothers: following the stripy elephant” has a quest where a player needs to open a refrigerator. There are $16$ handles on the refrigerator door. Every handle can be in one of t","description_type":"Markdown"},"platform":"Luogu","limit":{"time_limit":1000,"memory_limit":524288},"difficulty":{"LuoguStyle":"P4"},"is_remote":true,"is_sync":true,"sync_url":null,"sign":"LGP10456"},"statements":[{"statement_type":"Markdown","content":"The game “The Pilots Brothers: following the stripy elephant” has a quest where a player needs to open a refrigerator.\n\nThere are $16$ handles on the refrigerator door. Every handle can be in one of two states: open or closed. The refrigerator is open only when all handles are open. The handles are represented as a matrix $4\\times4$. You can change the state of a handle in any location $[i, j] (1 \\leq i, j \\leq 4)$. However, this also changes states of all handles in row $i$ and all handles in column $j$.\n\nThe task is to determine the minimum number of handle switching necessary to open the refrigerator.\n\n## Input\n\nThe input contains four lines. Each of the four lines contains four characters describing the initial state of appropriate handles. A symbol “+” means that the handle is in closed state, whereas the symbol “−” means “open”. At least one of the handles is initially closed.\n\n## Output\n\nThe first line of the input contains $N$ – the minimum number of switching. The rest $N$ lines describe switching sequence. Each of the lines contains a row number and a column number of the matrix separated by one or more spaces. If there are several solutions, you may give any one of them.\n\n[samples]","is_translate":false,"language":"English"}],"meta":{"iden":"LGP10456","tags":["2004","Special Judge","ICPC"],"sample_group":[["-+--\n----\n----\n-+--","6 \n1 1 \n1 3 \n1 4 \n4 1 \n4 3 \n4 4"]],"created_at":"2026-03-03 11:09:25"}}