How to add two matrix (size is define by user)

#include<iostream.h>

int main()
{
int l,m,z,n;
int matrixA[10][10];
int matrixB[10][10];
int matrixC[10][10];

cout<<"enter the dimension of the first matrix"<<endl;
cin>>l>>m;
cout<<"enter the dimension of the second matrix"<<endl;
cin>>z>>n;
if(m!=z||z!=m){
cout<<"error in the multiblication enter new dimensions"<<endl;
cout<<"enter the dimension of the first matrix"<<endl;
cin>>l>>m;
cout<<"enter the dimension of the second matrix"<<endl;
cin>>z>>n;
}

else{
cout<<"enter the first matrix"<<endl;
for(int i=0;i<l;i++){
for(int j=0;j<m;j++){
     cin>>matrixA[i][j];
     }
     }
cout<<"enter the second matrix"<<endl;
for(int i=0;i<z;i++){
for(int j=0;j<n;j++){
    cin>>matrixB[i][j];
}
}
for(int i=0;i<l;i++){
for(int j=0;j<n;j++){
        matrixC[i][j]=0;
        for(int k=0;k<m;k++){
matrixC[i][j]=matrixC[i][j]+(matrixA[i][k] * matrixB[k][j]);
}
}
}

cout<<"your matrix is"<<endl;
for(int i=0;i<l;i++){
for(int j=0;j<n;j++){
cout<<matrixC[i][j]<<" ";
}
cout<<endl;
}
}
//system("pause");
return 0;
}