import std.conv, std.functional, std.stdio, std.string; import std.algorithm, std.array, std.bigint, std.container, std.math, std.numeric, std.range, std.regex, std.typecons; import core.bitop; class EOFException : Throwable { this() { super("EOF"); } } string[] tokens; string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; } int readInt() { return readToken.to!int; } long readLong() { return readToken.to!long; } real readReal() { return readToken.to!real; } bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } } bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } } int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; } int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); } int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); } int N, K; string S; int solve() { int ret; auto a = S.map!(s => (s == '#')).array; int l = -1; foreach (i; 0 .. N) { if (a[i]) { l = i; break; } } assert(l != -1); int k = K; for (; k < l; ) { ++ret; ++k; a[k] = !a[k]; } for (; k > l; ) { ++ret; --k; a[k] = !a[k]; } int r = -1; foreach_reverse (i; 0 .. N) { if (a[i]) { r = i; break; } } if (r != -1) { int[] xs; if (a[l]) { xs ~= l; } foreach (i; l + 1 .. r) { if (!a[i]) { xs ~= i; } } debug { writefln("l = %s, r = %s, xs = %s", l, r, xs); } if (xs == [l]) { ret += 3; } else { ret += (r - l); foreach (j; 0 .. xs.length / 2) { ret += 2 * (xs[2 * j + 1] - xs[2 * j]); } if (xs.length % 2 != 0) { ret += 2 * (r - xs[$ - 1]) - 1; } } } debug { writeln("solve ", S, " ", K, " = ", ret); } return ret; } void main() { try { for (; ; ) { K = readInt() - 1; S = readToken(); N = cast(int)(S.length); int ans = 100 * N; foreach (dir; 0 .. 2) { chmin(ans, solve()); K = N - 1 - K; S = cast(string)(cast(ubyte[])(S).dup.reverse); } writeln(ans); } } catch (EOFException e) { } }