{"raw_statement":[{"iden":"problem statement","content":"You are given a string $S$ of length $N$ consisting of `X` and `Y`. You will choose $K$ characters at distinct positions in $S$ and change each of them: `X` becomes `Y` and `Y` becomes `X`. Find the maximum possible number of pairs of consecutive `Y`s in the resulting string."},{"iden":"constraints","content":"*   $1 \\leq N \\leq 2 \\times 10^5$\n*   $0 \\leq K \\leq N$\n*   $S$ is a string of length $N$ consisting of `X` and `Y`."},{"iden":"input","content":"The input is given from Standard Input in the following format:\n\n$N$ $K$\n$S$"},{"iden":"sample input 1","content":"5 1\nXYXYX"},{"iden":"sample output 1","content":"2\n\nYou will choose one character.\n\n*   If you choose the $1$\\-st character, the resulting string is `YYXYX`, with one pair of consecutive `Y`s at positions $1, 2$.\n*   If you choose the $2$\\-nd character, the resulting string is `XXXYX`, with no pair of consecutive `Y`s.\n*   If you choose the $3$\\-rd character, the resulting string is `XYYYX`, with two pairs of consecutive `Y`s at positions $2, 3$ and $3, 4$.\n*   If you choose the $4$\\-th character, the resulting string is `XYXXX`, with no pair of consecutive `Y`s.\n*   If you choose the $5$\\-th character, the resulting string is `XYXYY`, with one pair of consecutive `Y`s at positions $4, 5$.\n\nThus, the sought maximum number is $2$."},{"iden":"sample input 2","content":"5 4\nXYXYX"},{"iden":"sample output 2","content":"2\n\nIt is optimal to choose the $1$\\-st, $2$\\-nd, $3$\\-rd, and $5$\\-th characters to get `YXYYY`, or choose the $1$\\-st, $3$\\-rd, $4$\\-th, and $5$\\-th characters to get `YYYXY`. Note that you may not choose a character at the same position multiple times."}],"translated_statement":null,"sample_group":[],"show_order":["default"],"formal_statement":null,"simple_statement":null,"has_page_source":true}