import std.stdio, std.string, std.conv; import std.range, std.algorithm, std.array, std.math; void main() { int[int] a; string s; scan(s); int p; int ans; foreach (int i, ch; s) { if (ch == 'A') { p++; } else { p--; } if (p in a) { ans = max(ans, i - a[p]); } else { a[p] = i; } } writeln(ans); } void scan(T...)(ref T args) { import std.stdio : readln; import std.algorithm : splitter; import std.conv : to; import std.range.primitives; auto line = readln().splitter(); foreach (ref arg; args) { arg = line.front.to!(typeof(arg)); line.popFront(); } assert(line.empty); } void fillAll(R, T)(ref R arr, T value) { static if (is(typeof(arr[] = value))) { arr[] = value; } else { foreach (ref e; arr) { fillAll(e, value); } } }