fix: pairing cost formula (bluealloy#659)

* fix pairing cost formula bug

* chore: fmt

---------

Co-authored-by: Rohit Narurkar <rohit.narurkar@protonmail.com>

Author: 2 people

crates/precompile/src/bn128.rs

@@ -165,8 +165,7 @@ fn run_pair(
     pair_base_cost: u64,
     gas_limit: u64,
 ) -> PrecompileResult {
-    let gas_used =
-        pair_per_point_cost * input.len() as u64 / PAIR_ELEMENT_LEN as u64 + pair_base_cost;
+    let gas_used = (input.len() / PAIR_ELEMENT_LEN) as u64 * pair_per_point_cost + pair_base_cost;
     if gas_used > gas_limit {
         return Err(Error::OutOfGas);
     }