Consider the following row vectors

${}_1=(1,1,0,1,0,0),{}_2=(1,1,0,0,1,0)$

${}_3=(1,1,0,0,0,1),{}_4=(1,0,1,1,0,0)$

${}_5=(1,0,1,0,1,0),{}_6=(1,0,1,0,0,1)$

The dimension of the vector space spanned by these row vectors is