// URL: https://yukicoder.me/problems/no/743 import std.algorithm, std.array, std.container, std.math, std.range, std.typecons, std.string; version(unittest) {} else void main() { int N, M; io.getV(N, M); struct E { int a, b; } E[] e; io.getS!("a", "b")(N, e); foreach (ref ei; e) if (ei.a > ei.b) swap(ei.a, ei.b); e.sort!"a.a < b.a"; auto ft = fenwickTree!int(M), r = 0L; foreach (ei; e) { r += ft[ei.a..ei.b]; ++ft[ei.b]; } io.put(r); } class FenwickTree(T) { const size_t n; this(size_t n) { this.n = n; this.buf = new T[](n+1); } void opIndexOpAssign(string op)(T val, size_t i) if (op=="+"||op=="-") { ++i; for (; i <= n; i += i&-i) mixin("buf[i]"~op~"=val;"); } void opIndexUnary(string op)(size_t i) if (op=="++"||op=="--") { ++i; for (; i <= n; i += i&-i) mixin(op~"buf[i];"); } pure T opIndex(size_t i) { return opSlice(i, i+1); } pure T opSlice(size_t r, size_t l) { return get(l) - get(r); } pure size_t opDollar() { return n; } private { T[] buf; pure T get(size_t i) { auto s = T(0); for (; i > 0; i -= i & -i) s += buf[i]; return s; } } } FenwickTree!T fenwickTree(T)(size_t n) { return new FenwickTree!T(n); } auto io = IO!()(); import std.stdio; struct IO(alias IN = stdin, alias OUT = stdout) { import std.conv, std.format, std.meta, std.traits, core.stdc.stdlib; auto getV(T...)(ref T v) { foreach (ref w; v) get(w); } auto getA(T)(size_t n, ref T v) if (hasAssignableElements!T) { v = new T(n); foreach (ref w; v) get(w); } auto getC(T...)(size_t n, ref T v) if (allSatisfy!(hasAssignableElements, T)) { foreach (ref w; v) w = new typeof(w)(n); foreach (i; 0..n) foreach (ref w; v) get(w[i]); } auto getM(T)(size_t r, size_t c, ref T v) if (hasAssignableElements!T && hasAssignableElements!(ElementType!T)) { v = new T(r); foreach (ref w; v) getA(c, w); } template getS(E...) { auto getS(T)(size_t n, ref T v) { v = new T(n); foreach (ref w; v) foreach (e; E) mixin("get(w."~e~");"); } } auto put(alias conf = "{}", T...)(T v) { mixin("const PutConf c = "~conf~"; putMain!c(v);"); } auto putB(alias conf = "{}", S, T)(bool c, S t, T f) { if (c) put(t); else put(f); } auto putRaw(T...)(T v) { OUT.write(v); OUT.writeln; } private { dchar[] buf; auto sp = (new dchar[](0)).splitter; void nextLine() { IN.readln(buf); sp = buf.splitter; } auto get(T)(ref T v) { if (sp.empty) nextLine(); v = sp.front.to!T; sp.popFront(); } auto putMain(PutConf c, T...)(T v) { foreach (i, w; v) { putOne!c(w); if (i < v.length-1) OUT.write(c.delimiter); } static if (c.newline) OUT.writeln; static if (c.flush) OUT.flush(); static if (c.exit) exit(0); } auto putOne(PutConf c, T)(T v) { static if (isInputRange!T && !isSomeString!T) putRange!c(v); else if (isFloatingPoint!T) OUT.write(format(c.floatFormat, v)); else OUT.write(v); } auto putRange(PutConf c, T)(T v) { auto w = v; while (!w.empty) { putOne!c(w.front); w.popFront(); if (!w.empty) OUT.write(c.delimiter); } } } } const struct PutConf { bool newline = true, flush, exit; string floatFormat = "%.10f", delimiter = " "; }