import std.stdio, std.string, std.conv; import std.range, std.algorithm, std.array, std.typecons, std.container; import std.math, std.numeric, core.bitop; void main() { int a, b; scan(a, b); int ans; if (a % 3 + b % 3 == 0) { foreach (i ; a .. b + 1) { if (i % 3 == 0) { ans++; } } } else if ((a % 3 + b % 3) % 3 == 1) { foreach (i ; a .. b + 1) { if (i % 3 == 2) { ans++; } } } else { foreach (i ; a .. b + 1) { if (i % 3 == 1) { ans++; } } } 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); } } }