import std.stdio, std.conv, std.string, std.range, std.array, std.algorithm, std.math;

int main(){
	auto X = readln.strip.to!int;
	auto Y = readln.strip.to!int;
	auto L = readln.strip.to!int;
	
	if(Y>=0){
		if(X==0){
			num(Y,L).writeln;
		}else{
			(num(Y,L)+1+num(X,L)).writeln;
		}
	}else{
		(1+num(X,L)+1+num(Y,L)).writeln;
	}
	return 0;
}

int num(int n, int L){
	n=abs(n);
	return n==0 ? 0 : (n/L).to!int + (n%L == 0 ? 0 : 1);
}