diff --git a/main.go b/main.go
index <HASH>..<HASH> 100644
--- a/main.go
+++ b/main.go
@@ -39,7 +39,7 @@ var (
 var usage = `Usage: boom [options...] <url>
 
 Options:
-  -n	Number of requests to run.
+  -n	Number of requests to run. Can not be 
   -c	Number of requests to run concurrently. Total number of requests cannot
   	be smaller than the concurency level.
 
@@ -63,6 +63,10 @@ func main() {
 	n := *flagN
 	c := *flagC
 
+	if  n <= 0 || c <= 0 {
+		usageAndExit()
+	}
+
 	// If total number is smaller than concurrency level,
 	// make the total number c.
 	if c > n {
Sanity checks for n and c.