diff --git a/ex-4/main.c b/ex-4/main.c
index e0e1019..364bc1c 100644
--- a/ex-4/main.c
+++ b/ex-4/main.c
@@ -19,12 +19,12 @@ int parser(size_t *N, size_t *n, double *p_max, char argc, char **argv, size_t *
     else if (!strcmp(argv[i], "-o")) *go = 1;
     else
       {
-      fprintf(stderr, "Usage: %s -[hnbp]\n", argv[0]);
+      fprintf(stderr, "Usage: %s -[hnbpo]\n", argv[0]);
       fprintf(stderr, "\t-h\tShow this message.\n");
-      fprintf(stderr, "\t-n N\tThe number of events to generate. (default: 50000)\n");
+      fprintf(stderr, "\t-n N\tThe number of particles to generate. (default: 50000)\n");
       fprintf(stderr, "\t-b N\tThe number of bins of the histogram. (default: 50)\n");
       fprintf(stderr, "\t-p PMAX\tThe maximum value of momentum. (default: 10)\n");
-      fprintf(stderr, "\t-o \tPrint histogram to stdout.\n");
+      fprintf(stderr, "\t-o\tPrint histogram to stdout.\n");
       return 0;
       }
     }
@@ -42,7 +42,7 @@ int main(int argc, char **argv)
   double p_max = 10;
   size_t go = 0;
   int res = parser(&N, &n, &p_max, argc, argv, &go);
-  if (go == 0)
+  if (go == 0 && res == 1)
     {
     printf("\nGenerating histogram with:\n"
                        "%ld points\n"
@@ -145,12 +145,12 @@ int main(int argc, char **argv)
   func.function = &chi2;
   func.params = &params;
 
-  double min_p = 5;
-  double max_p = 15;
+  double min_p = p_max - 5;
+  double max_p = p_max + 5;
 
   // Initialize minimization.
   //
-  double x = 10;
+  double x = p_max;
   int    max_iter = 100;
   double prec = 1e-7;
   int    status = GSL_CONTINUE; 
diff --git a/makefile b/makefile
index 9df4aea..292f168 100644
--- a/makefile
+++ b/makefile
@@ -24,7 +24,7 @@ ex-4: ex-4/bin/main
 ex-4/bin/main: ex-4/main.c ex-4/lib.c
 	$(CCOMPILE)
 
-ex-5: ex-5/bin/casino ex-5/bin/manual ex-5/bin/trifecta
+ex-5: ex-5/bin/main
 ex-5/bin/%: ex-5/%.c
 	$(CCOMPILE)