Updated README

README.md

@@ -8,11 +8,42 @@ the hard work.
 
 # How?
 
-```bash
-python c2go.py tests/hello-world.c
+Let's use
+[prime.c](https://github.com/elliotchance/c2go/blob/master/tests/prime.c):
+
+```c
+#include <stdio.h>
+
+int main()
+{
+   int n, c;
+
+   printf("Enter a number\n");
+   scanf("%d", &n);
+
+   if ( n == 2 )
+      printf("Prime number.\n");
+   else
+   {
+       for ( c = 2 ; c <= n - 1 ; c++ )
+       {
+           if ( n % c == 0 )
+              break;
+       }
+       if ( c != n )
+          printf("Not prime.\n");
+       else
+          printf("Prime number.\n");
+   }
+   return 0;
+}
 ```
 
+```bash
+python c2go.py tests/prime.c
 ```
+
+```go
 package main
 
 import (
@@ -22,7 +53,24 @@ import (
 // ... lots of system types in Go removed for brevity.
 
 func main() {
-    fmt.Printf("Hello World\n")
+    var n int
+    var c int
+    fmt.Printf("Enter a number\n")
+    fmt.Scanf("%d", &n)
+    if n == 2 {
+        fmt.Printf("Prime number.\n")
+    } else {
+        for c = 2; c <= n - 1; c += 1 {
+            if n % c == 0 {
+                break
+            }
+        }
+        if c != n {
+            fmt.Printf("Not prime.\n")
+        } else {
+            fmt.Printf("Prime number.\n")
+        }
+    }
     return
 }
 ```