import std.algorithm, std.container, std.conv, std.math, std.range, std.typecons, std.stdio, std.string; auto rdsp(){return readln.splitter;} void pick(R,T)(ref R r,ref T t){t=r.front.to!T;r.popFront;} void readV(T...)(ref T t){auto r=rdsp;foreach(ref v;t)pick(r,v);} void readA(T)(size_t n,ref T[]t){t=new T[](n);auto r=rdsp;foreach(ref v;t)pick(r,v);} const inf = 10^^9+1; void main() { int n; readV(n); int[] a; readA(n, a); foreach (i; 0..n) a[i] -= i; auto b = a.filter!"a>0".array; auto m = a.length.to!int; auto dp = new int[](m); dp[] = inf; foreach (i; 0..m) { auto bs = dp.assumeSorted.lowerBound(b[i]+1); dp[bs.length] = b[i]; } writeln(n-dp.assumeSorted.lowerBound(inf).length.to!int); }