import std.conv, std.functional, std.range, std.stdio, std.string; import std.algorithm, std.array, std.bigint, std.complex, std.container, std.math, 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)); } long D; int Q; long[] A, B; void main() { try { for (; ; ) { D = readLong(); Q = readInt(); A = new long[Q]; B = new long[Q]; foreach (q; 0 .. Q) { A[q] = readLong(); B[q] = readLong() + 1; } alias P = Tuple!(long, long); auto set = new RedBlackTree!P; long ans; foreach (q; 0 .. Q) { long a = A[q], b = B[q]; auto r = set.lowerBound(P(B[q], D)); P[] rems; for (; !r.empty; r.popBack) { if (max(a, r.back[0]) <= min(b, r.back[1])) { rems ~= r.back; chmin(a, r.back[0]); chmax(b, r.back[1]); } else { break; } } foreach (p; rems) { set.removeKey(p); } set.insert(P(a, b)); debug { writeln("set = ", set); } chmax(ans, b - a); writeln(ans); } } } catch (EOFException e) { } }