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<b>let </b><font color="Maroon">c<sub>1</sub></font> be  non <a href="xboole_0.html#V1">zero</a> <a href="nat_1.html#NM1">Nat</a>;<br/><b>let </b><font color="Maroon">c<sub>2</sub></font> be    <a href="chain_1.html#M1" target="_self">Grating</a> of <font color="Maroon">c<sub>1</sub></font>;<br/><b>let </b><font color="Maroon">c<sub>3</sub></font> be    <a href="chain_1.html#M3" target="_self">Cycle</a> of <font color="Maroon">c<sub>1</sub></font>,<font color="Maroon">c<sub>2</sub></font>;<br/>





<b>consider </b><font color="Maroon">c<sub>4</sub></font> being   <a href="nat_1.html#NM1">Nat</a><b> such that </b><br/><a NAME="E2:101"/><i><font color="Green">E68</font></i>: 
<font color="Maroon">c<sub>1</sub></font> <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>4</sub></font> <a href="nat_1.html#K1">+</a> 1
 <b>by </b><i><a class="ref" href="nat_1.html#T22">NAT_1:22</a></i>;<br/>
<b>reconsider </b><font color="Maroon">c<sub>5</sub></font> = <font color="Maroon">c<sub>2</sub></font> as    <a href="chain_1.html#M1" target="_self">Grating</a> of <font color="Maroon">c<sub>4</sub></font> <a href="nat_1.html#K1">+</a> 1 <b>by </b><i><a class="txt" href="chain_1.html#E2:101"><i><font color="Green">E68</font></i></a></i>;<br/>
<b>reconsider </b><font color="Maroon">c<sub>6</sub></font> = <font color="Maroon">c<sub>3</sub></font> as    <a href="chain_1.html#M3" target="_self">Cycle</a> of <font color="Maroon">c<sub>4</sub></font> <a href="nat_1.html#K1">+</a> 1,<font color="Maroon">c<sub>5</sub></font> <b>by </b><i><a class="txt" href="chain_1.html#E2:101"><i><font color="Green">E68</font></i></a></i>;<br/>
<a NAME="E5:101"/>
 <a href="chain_1.html#K11" target="_self">del</a> <font color="Maroon">c<sub>6</sub></font> <a href="hidden.html#R1">=</a>  <a href="chain_1.html#K12" target="_self">0_</a> <font color="Maroon">c<sub>4</sub></font>,<font color="Maroon">c<sub>5</sub></font>
 
;<br/>
<a NAME="E6:101"/><b>then </b>
 <a href="chain_1.html#K11" target="_self">del</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>6</sub></font> <a href="subset_1.html#K3">`</a> </span>)</span> <a href="hidden.html#R1">=</a>  <a href="chain_1.html#K12" target="_self">0_</a> <font color="Maroon">c<sub>4</sub></font>,<font color="Maroon">c<sub>5</sub></font>
 
<b>by </b><i><a class="ref" href="chain_1.html#T64" target="_self">Th64</a></i>;<br/>
<b>hence </b><a NAME="E7:101"/>
<font color="Maroon">c<sub>3</sub></font> <a href="subset_1.html#K3">`</a>  is    <a href="chain_1.html#M3" target="_self">Cycle</a> of <font color="Maroon">c<sub>1</sub></font>,<font color="Maroon">c<sub>2</sub></font>
 <b>by </b><i><a class="txt" href="chain_1.html#E2:101"><i><font color="Green">E68</font></i></a>, <a class="ref" href="chain_1.html#T66" target="_self">Th66</a></i>;<br/>


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