Use correct formula
Use correct formula

rust-lang/num,rust-num/num,rust-lang/num,rust-num/num-traits,rust-num/num-integer,DonSheddow/num,koverstreet/num,rust-num/num-traits,rust-num/num-bigint,koverstreet/num,rust-num/num-integer,rust-num/num-bigint,DonSheddow/num,rust-num/num