How to use MultiSum function in Modelica?

I've got a vector with a size of 5 and would like to sum each of its elements at each step in a variable (summ), but I don't know how to use MultiSum function in this case.

model add
import Modelica.Blocks.Math.MultiSum;
Real k[5]={1,2,3,4,5};
Real summ;
equation
for i in 1:4 loop
summ = MultiSum(???)
end for;

end add;

I would appreciate if you could help.

Solution

The solution by MarkusA is good, but if you really wanted to use the block you could do something like this:

model add
  import Modelica.Blocks.Math.MultiSum;
  Real k[5]={1,2,3,4,5};
  Modelica.Blocks.Sources.RealExpression realExpression[size(k, 1)](y=k);
  Modelica.Blocks.Interfaces.RealOutput summ;
  MultiSum multiSum(nu=size(k, 1));
equation
  connect(multiSum.y, summ);
  connect(realExpression.y, multiSum.u);
end add;

or with annotations:

model add
  import Modelica.Blocks.Math.MultiSum;
  Real k[5]={1,2,3,4,5};
  Modelica.Blocks.Sources.RealExpression realExpression[size(k, 1)](y=k)
    annotation (Placement(transformation(extent={{-110,16},{-90,36}})));
  Modelica.Blocks.Interfaces.RealOutput summ
    annotation (Placement(transformation(extent={{86,4},{106,24}})));
  MultiSum multiSum(nu=size(k, 1))
    annotation (Placement(transformation(extent={{-10,20},{2,32}})));
equation 
  connect(multiSum.y, summ) annotation (Line(points={{3.02,26},{80,26},{80,14},{
          96,14}}, color={0,0,127}));
  connect(realExpression.y, multiSum.u)
    annotation (Line(points={{-89,26},{-10,26}}, color={0,0,127}));
  annotation (uses(Modelica(version="4.0.0")));
end add;