diff --git a/powersoftau/src/bin/beacon_constrained.rs b/powersoftau/src/bin/beacon_constrained.rs
index e63c091..90ec337 100644
--- a/powersoftau/src/bin/beacon_constrained.rs
+++ b/powersoftau/src/bin/beacon_constrained.rs
@@ -19,8 +19,8 @@ const CHECK_INPUT_CORRECTNESS: CheckForCorrectness = CheckForCorrectness::No;
 #[allow(clippy::modulo_one)]
 fn main() {
     let args: Vec<String> = std::env::args().collect();
-    if args.len() != 6 {
-        println!("Usage: \n<challenge_file> <response_file> <circuit_power> <batch_size> <beacon_hash>");
+    if args.len() != 7 {
+        println!("Usage: \n<challenge_file> <response_file> <circuit_power> <batch_size> <beacon_hash> <num_iterations_exp>");
         std::process::exit(exitcode::USAGE);
     }
     let challenge_filename = &args[1];
@@ -28,6 +28,12 @@ fn main() {
     let circuit_power = args[3].parse().expect("could not parse circuit power");
     let batch_size = args[4].parse().expect("could not parse batch size");
     let beacon_hash = &args[5];
+    let num_iterations_exp = &args[6].parse::<usize>().unwrap();
+
+    if *num_iterations_exp < 10 || *num_iterations_exp > 63 {
+        println!("in_num_iterations_exp should be in [10, 63] range");
+        std::process::exit(exitcode::DATAERR);
+    }
 
     let parameters = CeremonyParams::<Bn256>::new(circuit_power, batch_size);
 
@@ -51,14 +57,14 @@ fn main() {
         let mut cur_hash = hex::decode(beacon_hash).unwrap();
 
         // Performs 2^n hash iterations over it
-        const N: u64 = 10;
+        let n: usize = *num_iterations_exp;
 
-        for i in 0..(1u64 << N) {
+        for i in 0..(1u64 << n) {
             // Print 1024 of the interstitial states
             // so that verification can be
             // parallelized
 
-            if i % (1u64 << (N - 10)) == 0 {
+            if i % (1u64 << (n - 10)) == 0 {
                 print!("{}: ", i);
                 for b in cur_hash.iter() {
                     print!("{:02x}", b);
diff --git a/powersoftau/test.sh b/powersoftau/test.sh
index 5ad637b..c9567bf 100755
--- a/powersoftau/test.sh
+++ b/powersoftau/test.sh
@@ -21,7 +21,7 @@ cargo run --release --bin verify_transform_constrained challenge2 response2 chal
 yes | cargo run --release --bin compute_constrained challenge3 response3 $SIZE $BATCH
 cargo run --release --bin verify_transform_constrained challenge3 response3 challenge4 $SIZE $BATCH
 
-cargo run --release --bin beacon_constrained challenge4 response4 $SIZE $BATCH 0000000000000000000a558a61ddc8ee4e488d647a747fe4dcc362fe2026c620
+cargo run --release --bin beacon_constrained challenge4 response4 $SIZE $BATCH 0000000000000000000a558a61ddc8ee4e488d647a747fe4dcc362fe2026c620 10
 cargo run --release --bin verify_transform_constrained challenge4 response4 challenge5 $SIZE $BATCH
 
 cargo run --release --bin prepare_phase2 response4 $SIZE $BATCH