diff --git a/compile.sh b/compile.sh
index 01e3b07..1b05d44 100644
--- a/compile.sh
+++ b/compile.sh
@@ -1,6 +1,6 @@
 #!/bin/bash
 
-mkdir build
+mkdir -p build
 cd build
 cmake ..
 make -j
diff --git a/example.cpp b/example.cpp
index 9bc1dee..fadd57c 100644
--- a/example.cpp
+++ b/example.cpp
@@ -1,8 +1,14 @@
 #include <iostream>
 #include <opencv2/core.hpp>
+#include <sys/stat.h>
 
 using namespace std;
 using namespace cv;
+
+inline bool file_exists (const std::string& name) {
+  struct stat buffer;   
+  return (stat (name.c_str(), &buffer) == 0); 
+}
   
 int main(int argc, char** argv)
 {
@@ -11,14 +17,19 @@ int main(int argc, char** argv)
     if (argc == 2) {
         input = argv[1];
     } else if (argc < 2) {
-        cerr << "Please provide one image" << endl;
+        cerr << "Please provide one image." << endl;
         return -1;
     } else if (argc > 2) {
-        cerr << "Please provide only one image" << endl;
+        cerr << "Please provide only one image." << endl;
         return -2;
     }
 
-    cout << "Using image " << input << endl;
+    if (!file_exists(input)) {
+        cerr << "File " << input << " does not exist." << endl;
+        return -3;
+    }
+
+    cout << "Using image " << input << "." << endl;
   
     return 0;
 }
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