diff --git a/lib/report/.gitkeep b/lib/report/.gitkeep
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diff --git a/readme.md b/readme.md
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--- /dev/null
+++ b/readme.md
@@ -0,0 +1,16 @@
+# 斐波那契数列计算函数
+
+用于斐波那契数列中第N个元素的值，在报表模板中设置格子的值为公式：
+
+```
+=Fibonacci(50)
+
+```
+
+模板设置如图所示：
+
+![tpl](screenshots/1.png)
+
+报表展示结果如下图所示：
+
+![show](screenshots/2.png)
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diff --git a/src/main/java/com/fr/plugin/function/fib/Fibonacci.java b/src/main/java/com/fr/plugin/function/fib/Fibonacci.java
index 3291059..e7494ec 100644
--- a/src/main/java/com/fr/plugin/function/fib/Fibonacci.java
+++ b/src/main/java/com/fr/plugin/function/fib/Fibonacci.java
@@ -24,7 +24,7 @@ public class Fibonacci extends AbstractFunction {
         return getFib(n);
     }
 
-    private int getFib(int n) {
+    private long getFib(int n) {
         if (n < 0) {
             return -1;
         } else if (n == 0) {
@@ -32,7 +32,7 @@ public class Fibonacci extends AbstractFunction {
         } else if (n == 1 || n == 2) {
             return 1;
         } else {
-            int[] fibAry = new int[n + 1];
+            long[] fibAry = new long[n + 1];
             fibAry[0] = 0;
             fibAry[1] = fibAry[2] = 1;
             for (int i = 3; i <= n; i++) {