diff --git a/Makefile b/Makefile
index 1f6d2d5..ac51a3e 100644
--- a/Makefile
+++ b/Makefile
@@ -6,7 +6,7 @@ CURTIME := $(shell date +%s) # current system time in UNIX
 launch:
 	@rm -rf output.txt
 	@./scripts/generate_config.sh ${NODES}
-	./scripts/launch_with_X_nodes.sh ${NODES} ${F} ${CURTIME} &
+	./scripts/launch_with_X_nodes.sh ${NODES} ${F} ${CURTIME} 
 
 # launch-default launches a protocol with 1 leader and 9 followers
 # sets F to 8 (hence, 8 Byzantine nodes can be tolerated)
diff --git a/README.md b/README.md
index cfbea18..785013f 100644
--- a/README.md
+++ b/README.md
@@ -37,8 +37,13 @@ where `X` is a number of nodes and `Y` is a number of Byzantine nodes a protocol
 (in other words, a number of stages a protocol will execute).
 
 Note: available values for `Y`: [0; X-2].
+
 Reason: there should be at least 2 honest nodes in the system.
 
+Note#2: available values for `X`: 3+.
+
+Reason: there should be at least 3 nodes in the consensus instance (otherwise, it's trivial).
+
 ### Default way
 
 To run a protocol in default mode, execute:
diff --git a/scripts/launch_with_X_nodes.sh b/scripts/launch_with_X_nodes.sh
index ab7b8f2..af97966 100755
--- a/scripts/launch_with_X_nodes.sh
+++ b/scripts/launch_with_X_nodes.sh
@@ -4,6 +4,18 @@ num_of_nodes=$1
 F=$2
 curtime=$3
 
+upperbound_F=$(($num_of_nodes - 2))
+
+if [ $num_of_nodes -lt 3 ]; then
+    echo -e "\033[31mERROR:\033[0m Number of nodes should be at least 3: got $num_of_nodes, expected 3 or more" >&2
+    exit 1
+fi
+
+if [ $F -gt $upperbound_F ]; then
+    echo -e "\033[31mERROR:\033[0m F should not be set to more than number of nodes - 2: got $F, expected $upperbound_F or less" >&2
+    exit 1
+fi
+
 cargo run $(pwd)/config.txt 0 $F $curtime & # launch leader
 
 for ((i=1; i<$num_of_nodes; i++))