diff --git a/069_sqrt/Makefile b/069_sqrt/Makefile
new file mode 100644
index 0000000..3d94c52
--- /dev/null
+++ b/069_sqrt/Makefile
@@ -0,0 +1,2 @@
+all:
+	gcc -O2 -o test sqrt.c
diff --git a/069_sqrt/sqrt.c b/069_sqrt/sqrt.c
new file mode 100644
index 0000000..1d3a5c3
--- /dev/null
+++ b/069_sqrt/sqrt.c
@@ -0,0 +1,35 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+static int mySqrt(int x)
+{
+    if (x == 0) {
+        return 0;
+    }
+
+    unsigned int left = 1;
+    unsigned int right = (unsigned int) x;
+    for (; ;) {
+        unsigned int mid = left + (right - left) / 2;
+        if (mid > x/mid) {
+            right = mid;
+        } else {
+            if (mid + 1 > x/(mid + 1)) {
+                return mid;
+            } else {
+                left = mid;
+            }
+        }
+    }
+}
+
+int main(int argc, char **argv)
+{
+    if (argc != 2) {
+        fprintf(stderr, "Usage: ./test n\n");
+        exit(-1);
+    }
+
+    printf("%d\n", mySqrt(atoi(argv[1])));
+    return 0;
+}