diff --git a/ex-2/fast.c b/ex-2/fast.c
index 22a2b33..da72e7b 100644
--- a/ex-2/fast.c
+++ b/ex-2/fast.c
@@ -2,6 +2,7 @@
 #include <stdlib.h>
 #include <math.h>
 #include <gmp.h>
+#include <time.h>
 
 /* The Euler-Mascheroni constant is here computed to
  * arbitrary precision using GMP floating point numbers
@@ -216,7 +217,12 @@ int main(int argc, char** argv) {
   mpf_set_default_prec(prec + 64);
 
   mpf_t y; mpf_init(y);
+
+  clock_t begin = clock();
   mpf_gamma(y, digits);
+  clock_t end = clock();
+  double time = (double)(end - begin)/CLOCKS_PER_SEC;
+  fprintf(stderr, "[main] running time: %gs\n", time);
 
   // again, trick to avoid rounding
   gmp_printf("%.*Ff\b \n", digits+1, y);