diff --git a/homework2/src/main.cc b/homework2/src/main.cc
index 869b260..66fdf41 100644
--- a/homework2/src/main.cc
+++ b/homework2/src/main.cc
@@ -1,19 +1,44 @@
 //main
 
 #include "ComputeArithmetic.hh"
 #include "ComputePi.hh"
 #include <iostream>
+#include <sstream>
 
 using namespace std;
 
-int main(){
+int main(int argc, char ** argv){
 
-    unsigned N=500;
+    //command line arguments: Type of series and N of terms.
 
-    ComputePi my_serie;
-    double tmp = my_serie.compute(N);
+    stringstream sstr;
+    for (int i = 1 ; i < argc ; ++i){
+        sstr << argv[i] << " ";
+    }
 
-    cout<<"Result for the arithmetic series with "<<N<<" terms is "<< tmp<<endl;
+    string which_series;
+    unsigned N;
+    sstr >> which_series;
+    sstr >> N;
 
+    Series * my_series = NULL;
+
+    if (which_series == "pi")
+        my_series = new ComputePi();
+    else if (which_series == "arithmetic")
+        my_series = new ComputeArithmetic();
+    else {
+        cout<<"insert one of the two available options:"
+              "\n\t arithmetic (to compute arithmetic series)"
+              "\n\t pi (to compute Pi series)"<<endl;
+        return EXIT_FAILURE;
+    }
+
+
+    double tmp = my_series->compute(N);
+
+    cout<<"Result for the "<<which_series<<" series with "<<N<<" terms is "<< tmp<<endl;
+
+    delete my_series;
     return 0;
 }