diff --git a/230124-sampen/sampen.cpp b/230124-sampen/sampen.cpp
index 185bc002743918f59b5cdef1c7342fa578134947..9a4899399675ede043214bcbdf3d7423e84aa921 100644
--- a/230124-sampen/sampen.cpp
+++ b/230124-sampen/sampen.cpp
@@ -107,21 +107,21 @@ double FastSampEn_ai(double *X, int N, int m, double r)
                     D = t;
             }
             if (D <= r)
-                Ai++;
+                Bi++;
             if (j < N - m) {
                 double t = fabs(X[i + m] - X[j + m]);
                 if (t > D)
                     D = t;
                 if (D <= r)
-                    Bi++;
+                    Ai++;
             }
         }
     }
-    double s1 = 1.0 * Ai / ((N - m + 1) * (N - m) / 2);
-    double s2 = 1.0 * Bi / ((N - m) * (N - m - 1) / 2);
-    if (s1 == 0 || s2 == 0)
+    double B = 1.0 * Bi / ((N - m + 1) * (N - m) / 2);
+    double A = 1.0 * Ai / ((N - m) * (N - m - 1) / 2);
+    if (A == 0 || B == 0)
         return 0;
-    return -log(s2 / s1);
+    return -log(A / B);
 }
 
 double FastSampEn_ai_m2(double* X, int N, double r)
@@ -135,19 +135,19 @@ double FastSampEn_ai_m2(double* X, int N, double r)
             if (t > D)
                 D = t;
             if (D <= r)
-                Ai++;
+                Bi++;
             if (j < N - 2) {
                 double t = fabs(X[i + 2] - X[j + 2]);
                 if (t > D)
                     D = t;
                 if (D <= r)
-                    Bi++;
+                    Ai++;
             }
         }
     }
-    double s1 = 1.0 * Ai / ((N - 1) * (N - 2) / 2);
-    double s2 = 1.0 * Bi / ((N - 2) * (N - 3) / 2);
-    if (s1 == 0 || s2 == 0)
+    double B = 1.0 * Bi / ((N - 1) * (N - 2) / 2);
+    double A = 1.0 * Ai / ((N - 2) * (N - 3) / 2);
+    if (A == 0 || B == 0)
         return 0;
-    return -log(s2 / s1);
+    return -log(A / B);
 }