reserve GS for GraphStruct;
reserve G,G1,G2,G3 for _Graph;
reserve e,x,x1,x2,y,y1,y2,E,V,X,Y for set;
reserve n,n1,n2 for Nat;
reserve v,v1,v2 for Vertex of G;

theorem
  for G being _finite _Graph holds G.order() >= 1
proof
  let G be _finite _Graph;
  0+1 < G.order()+1 by NAT_1:3,XREAL_1:8;
  hence thesis by NAT_1:13;
end;
