diff --git a/build.gradle.kts b/build.gradle.kts
index b5dab57..753fbbb 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -4,7 +4,7 @@ plugins {
 }
 
 group = "net.sergeych"
-version = "0.0.4-SNAPSHOT"
+version = "0.0.5-SNAPSHOT"
 
 repositories {
     mavenCentral()
@@ -43,7 +43,7 @@ kotlin {
         val commonMain by getting {
             dependencies {
                 implementation("dev.gitlive:kotlin-diff-utils:4.1.4")
-                implementation("net.sergeych:mp_stools:[1.3.3,)")
+                implementation("net.sergeych:mp_stools:[1.3.4,)")
             }
         }
         val commonTest by getting {
diff --git a/src/commonMain/kotlin/net.sergeych.merge3/merge3.kt b/src/commonMain/kotlin/net.sergeych.merge3/merge3.kt
index 9957bfd..27fe4ba 100644
--- a/src/commonMain/kotlin/net.sergeych.merge3/merge3.kt
+++ b/src/commonMain/kotlin/net.sergeych.merge3/merge3.kt
@@ -13,20 +13,23 @@ import net.sergeych.sprintf.sprintf
  *
  * @param merged the best merged data. In the case of the conflict usually has both variants concatennated in place
  * @param changedAreas ranges where data were altered. could be used to highlight changes
+ * @param sourceIndices indexes of items in source array (not included in result) in new result [merged]. If source
+ *          item is not included int the merged array, its index will be -1
  */
 class MergeResult<T>(
-    val merged: List<T>,
+    val merged: MutableList<T>,
     val changedAreas: List<IntRange>,
+    val sourceIndices: MutableList<Int>,
 ) {
     val blocks: List<MergedBlock<T>> by lazy {
         if (changedAreas.isEmpty())
-            listOf(MergedBlock.Unchanged(merged))
+            listOf(MergedBlock.Unchanged(merged, sourceIndices[0]))
         else {
             val result = mutableListOf<MergedBlock<T>>()
             var start = 0
             for (r in changedAreas) {
                 if (start != r.start) {
-                    result.add(MergedBlock.Unchanged(merged.slice(start until r.start)))
+                    result.add(MergedBlock.Unchanged(merged.slice(start until r.start), sourceIndices[start]))
                 }
                 if (!r.isEmpty()) {
                     result.add(MergedBlock.Resolved(merged.slice(r)))
@@ -34,11 +37,21 @@ class MergeResult<T>(
                 start = r.endInclusive + 1
             }
             if (start < merged.size) {
-                result.add(MergedBlock.Unchanged(merged.slice(start until merged.size)))
+                result.add(MergedBlock.Unchanged(merged.slice(start until merged.size), sourceIndices[start]))
             }
             result
         }
     }
+
+    fun toTrace(source: List<T>): String {
+        val r = StringBuilder()
+        r.append(merged.indices.joinToString("") { "%3d".sprintf(it) } + "\n")
+        r.append(merged.joinToString("") { "%3s".sprintf(it) } + "\n")
+        r.append("---- source ----\n")
+        r.append(source.joinToString("") { "%3s".sprintf(it) } + "\n")
+        r.append(sourceIndices.joinToString("") { "%3s".sprintf(it) } + "\n")
+        return r.toString()
+    }
 }
 
 /**
@@ -52,8 +65,9 @@ sealed class MergedBlock<T> {
 
     /**
      * Data that are equals in both variants and therefore was not altered
+     * @param referenceIndex index if the first item of the unchanged data as it was in source array.
      */
-    data class Unchanged<T>(override val data: List<T>) : MergedBlock<T>()
+    data class Unchanged<T>(override val data: List<T>, val referenceIndex: Int) : MergedBlock<T>()
 
     /**
      * The portion of data that was merged without conflicts
@@ -74,16 +88,18 @@ sealed class MergedBlock<T> {
 /**
  * Perform 3-way merge. See [merge3] for details.
  */
-private class Merge3<T>(val source: List<T>, val variantA: List<T>, val variantB: List<T>,
-    val showDebug: Boolean = false) {
+private class Merge3<T>(
+    val source: List<T>, val variantA: List<T>, val variantB: List<T>,
+    val showDebug: Boolean = false,
+) {
 
     private val reindex = source.indices.toMutableList()
     private val changeCount = MutableList(source.size) { 0 }
 
     val result = source.toMutableList()
 
-    private fun debug( f: ()-> String ) {
-        if( showDebug ) println(f())
+    private fun debug(f: () -> String) {
+        if (showDebug) println(f())
     }
 
     private fun trace() {
@@ -253,7 +269,7 @@ private class Merge3<T>(val source: List<T>, val variantA: List<T>, val variantB
 //        closeConflict(changeCount.size)
         closeUpdate(changeCount.size)
 
-        return MergeResult<T>(result, updates)
+        return MergeResult<T>(result, updates, reindex)
     }
 }
 
diff --git a/src/commonTest/kotlin/testMerge.kt b/src/commonTest/kotlin/testMerge.kt
index 6cdd1b8..f323499 100644
--- a/src/commonTest/kotlin/testMerge.kt
+++ b/src/commonTest/kotlin/testMerge.kt
@@ -22,7 +22,7 @@ class BasicTest {
     @Test
     fun testMergeNoConflicts3() {
         Log.connectConsole()
-        val src = "1Hello, world!".toList()
+        val src = "Hello, world!".toList()
         val a = "Hello, friend!".toList()
         val b = "Bye world!".toList()
 
@@ -31,6 +31,7 @@ class BasicTest {
 //        println(m.conflicts)
         println(m.changedAreas)
         assertEquals("Bye friend!", m.merged.str)
+        println(m.toTrace(src))
 //        assertTrue(m.noConflicts)
     }