How can i make arrows like this?
This is what I've done so far.
\documentclass[10pt,a4paper]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[left=22mm,bottom=22mm,right=28mm,top=30mm]{geometry}
\usepackage{tikz}
\usetikzlibrary{shapes,arrows}
\begin{document}
\pagestyle{empty}
% Define block styles
\tikzstyle{decision} = [diamond, draw, fill=blue!20,
text width=4.5em, text badly centered, node distance=3cm, inner sep=0pt]
\tikzstyle{block} = [rectangle, draw, fill=blue!20,
text width=2cm, text centered, rounded corners, minimum height=10mm]
\tikzstyle{line} = [draw, -latex']
\tikzstyle{cloud} = [draw, ellipse,fill=red!20, node distance=3cm,
minimum height=2em]
\begin{center}
\begin{tikzpicture}[node distance = 3.4cm, auto]
\node [block,yshift=30mm] (1) {1};
\node [block, xshift=-30mm] (2) {2};
\node[block, xshift=-60mm] (3) {3};
\node [block, xshift=-90mm] (4) {4};
\node [block, xshift=-120mm] (5) {5};
\node [block,yshift=30mm, xshift=-45mm] (6) {6};
\node [block,yshift=-40mm, xshift=-105mm] (7) {7};
\node [block,yshift=-60mm, xshift=-105mm] (8) {8};
\node [block,yshift=-25mm, xshift=-75mm] (9) {9};
\node[block, xshift=-60mm,yshift=-60mm] (10) {10};
\node [block, xshift=-30mm,yshift=-60mm] (11) {11};
\node[block, xshift=0mm,yshift=-60mm] (12) {12};
\draw[->,>=latex'] (4) -- (3);
\draw[->,>=latex'] (3) -- (2);
\end{tikzpicture}
\end{center}
\end{document}