diff --git a/Homework2/src/compute_pi.hh b/Homework2/src/compute_pi.hh
index e69de29..9585f5b 100644
--- a/Homework2/src/compute_pi.hh
+++ b/Homework2/src/compute_pi.hh
@@ -0,0 +1,12 @@
+#ifndef COMPUTE_PI_HH
+#define COMPUTE_PI_HH
+
+#include "series.hh"
+
+class compute_pi: public Series
+{
+public:
+    double compute(unsigned int N);
+};
+
+#endif
diff --git a/Homework2/src/main.cc b/Homework2/src/main.cc
index 0bc725f..2cceb55 100644
--- a/Homework2/src/main.cc
+++ b/Homework2/src/main.cc
@@ -1,20 +1,21 @@
 #include <iostream>
 #include <string>
+#include <math.h>
 #include "compute_arithmetic.hh"
 
 int main(int argc, char ** argv)
 {
     std::string serie_type = argv[1];
-    unsigned long N = atof (argv[2]); // max number of iteration entered as input
+    unsigned long N = abs(atof (argv[2])); // max number of iteration entered as input
 
     if (serie_type == "arithmetic") {
         compute_arithmetic my_serie;
         double result = my_serie.compute(N); // sum over 10
         std::cout << result << std::endl;
     } else {
         std::cout << "Serie type not implemented yet" << std::endl;
         abort();
     }
 
     return 0;
 }