diff --git a/Bin2Root.cpp b/Bin2Root.cpp
index 65bb485..0e8e299 100644
--- a/Bin2Root.cpp
+++ b/Bin2Root.cpp
@@ -52,30 +52,40 @@ std::vector<std::pair<int, int64_t>> readFileAndExtractData(const std::string& f
   return data;
 }
 
-int extractDigiSN(const std::string& str) {
-    std::size_t firstUnderscore = str.find('_');
-    if (firstUnderscore == std::string::npos) {
-        return -1;  // No first underscore found, return an error value
-    }
+// Function to extract the number between the n-th and (n+1)-th underscore
+int extractDigiSN(const std::string& str, int n = 1) {
+  std::size_t pos = 0;
 
-    std::size_t secondUnderscore = str.find('_', firstUnderscore + 1);
-    if (secondUnderscore == std::string::npos) {
-        return -1;  // No second underscore found, return an error value
+  // Find the position of the n-th underscore
+  for (int i = 0; i < n; ++i) {
+    pos = str.find('_', pos);
+    if (pos == std::string::npos) {
+      std::cerr << "Less than " << n << " underscores in the string." << std::endl;
+      return -1;  // Return error if there are fewer underscores than expected
     }
+    ++pos;  // Move to the next character after the underscore
+  }
 
-    // Extract the substring between the first and second underscores
-    std::string extracted = str.substr(firstUnderscore + 1, secondUnderscore - firstUnderscore - 1);
-    
-    // Convert the extracted string to an integer using std::stoi
-    try {
-        return std::stoi(extracted);
-    } catch (const std::invalid_argument& e) {
-        std::cerr << "Invalid number format: " << extracted << std::endl;
-        return -1;  // Return an error value on conversion failure
-    } catch (const std::out_of_range& e) {
-        std::cerr << "Number out of range: " << extracted << std::endl;
-        return -1;  // Return an error value if the number is too large
-    }
+  // Find the position of the (n+1)-th underscore
+  std::size_t nextUnderscore = str.find('_', pos);
+  if (nextUnderscore == std::string::npos) {
+    std::cerr << "No (n+1)-th underscore found." << std::endl;
+    return -1;  // Return error if there's no (n+1)-th underscore
+  }
+
+  // Extract the substring between the n-th and (n+1)-th underscores
+  std::string extracted = str.substr(pos, nextUnderscore - pos);
+  
+  // Convert the extracted substring to an integer using std::stoi
+  try {
+    return std::stoi(extracted);
+  } catch (const std::invalid_argument& e) {
+    std::cerr << "Invalid number format: " << extracted << std::endl;
+    return -1;  // Return an error value on conversion failure
+  } catch (const std::out_of_range& e) {
+    std::cerr << "Number out of range: " << extracted << std::endl;
+    return -1;  // Return an error value if the number is too large
+  }
 }
 
 //^#############################################################
@@ -96,7 +106,8 @@ int main(int argc, char **argv) {
     printf("          %s 100 0  '\\ls -1 *001*.bin' (event build with 100 ns, no trace, no verbose)\n", argv[0]);
     printf("\n");
     printf(" Time offset file format :\n");
-    printf("[digi ID]   [time offset(int64_t)]\n");
+    printf("[n, sn appears between the n-th - (n+1)-th underscore of the fileName]   0\n");
+    printf("[digi sn]   [time offset(int64_t)]\n");
     printf("\n");
     printf(" file name should be this format CH0@V1725_324_Data_run_196.bin\n");
     printf("     so that the serial number is between the 1st and 2nd underscore\n");
@@ -138,6 +149,7 @@ int main(int argc, char **argv) {
   }
 
   std::vector<std::pair<int, int64_t>> timeOffsetList ;
+  timeOffsetList.clear();
 
   printf("-------> Out file name : %s \n", outFileName.Data());
   printf("=========================================\n"); 
@@ -160,9 +172,11 @@ int main(int argc, char **argv) {
   for(int i = 0; i < nFile; i++ ){
     printf(">>>>>>>> %2d | %s \n", i, inFileName[i].Data());
     reader[i].OpenFile(inFileName[i]);
-    for (size_t i = 0 ; timeOffsetList.size(); i++) {
-      int sn = extractDigiSN(inFileName[i].Data());
-      if( sn == timeOffsetList[i].first ) reader[i].SetTimeOffset(timeOffsetList[i].second);
+    if( timeOffsetList.size() > 1 ){
+      for (size_t i = 1 ; timeOffsetList.size(); i++) {
+        int sn = extractDigiSN(inFileName[i].Data(), timeOffsetList[0].first);
+        if( sn == timeOffsetList[i].first ) reader[i].SetTimeOffset(timeOffsetList[i].second);
+      }
     }
     reader[i].ScanNumHit();
     totalHitCount += reader[i].GetNumHit();
diff --git a/timeOffset.txt b/timeOffset.txt
new file mode 100644
index 0000000..fdd4258
--- /dev/null
+++ b/timeOffset.txt
@@ -0,0 +1,4 @@
+1    0 
+123   456
+86    49
+19267 0
\ No newline at end of file