Decision Optimization

My CPLEX code gives me this message. Can someone help me finding the problem? I cannot find anything wrong.

/*********************************************
* OPL 12.6.0.0 Model
* Author: Puno
* Creation Date: 01.02.2018 at 11:41:34
*********************************************/

// problem size
int n = 50; // no of demand nodes
int f = 4; // no of acility locations
int p = 4; // no of facilities

// indices
range I = 1..n; // demand node index
range J = 1..f; // facility location index x axis
range K = 1..f; // facility location index y axis
// parameters
int d[I][J][K] = [[25,93,36,98,100,22,63,3,96,62,16,49,66,79,44,37,94,89,4,93,81,27,48,48,73,30,7,8,90,96,91,53,15,26,65,63,54,44,46,69,70,84,87,2,15,67,81,32,25,37
], // distances between facility locations and demand nodes
[9,0,13,19,17,26], // in this example, each demand node is a potential location
[12,13,0,8,7,15],
[10,19,8,0,13,7],
[19,17,7,13,0,9],
[17,26,15,7,9,0]];

// decision variable
dvar boolean y[I][J][K]; // binary indicator, if node i is assigned to facility j
dvar boolean x[J]; // binary indicator, if facility j is selected
dvar int z;

// objective function
minimize z;

// constraints
subject to{
// each demand node must be assigned to a facility
forall(i in I)
sum(j in J) y[i][j] == 1;

// demand nodes can only be assigned to selected facilities
forall(j in J, i in I)
y[i][j] - x[j] <= 0;

// p facilities must be selected
sum(j in J) x[j] == p;

// calculation of maximum distance from a facility to a node
forall(i in I)
sum(j in J) d[i][j][k] * y[i][j][k] <= z;
}