import std.conv, std.functional, std.range, std.stdio, std.string; import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, 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)); } // floor(sqrt(a)) long floorSqrt(long a) { import core.bitop : bsr; import std.algorithm : min; long b = a, x = 0, y = 0; for (int e = bsr(a) & ~1; e >= 0; e -= 2) { x <<= 1; y <<= 1; if (b >= (y | 1) << e) { b -= (y | 1) << e; x |= 1; y += 2; } } return x; } void main() { try { for (; ; ) { const N = readLong(); const k = floorSqrt(N); long ans = k + k; if (N < k * (k + 1)) { --ans; } writeln(ans); debug { bool[long] app; foreach (i; 1 .. N + 1) { app[N / i] = true; } const brt = cast(long)(app.length); writeln("brt = ", brt); assert(brt == ans); } } } catch (EOFException e) { } }