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diff --git a/src/boost/libs/contract/example/n1962/sqrt.cpp b/src/boost/libs/contract/example/n1962/sqrt.cpp
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+++ b/src/boost/libs/contract/example/n1962/sqrt.cpp
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+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+//[n1962_sqrt
+#include <boost/contract.hpp>
+#include <cmath>
+#include <cassert>
+
+long lsqrt(long x) {
+    long result;
+    boost::contract::check c = boost::contract::function()
+        .precondition([&] {
+            BOOST_CONTRACT_ASSERT(x >= 0);
+        })
+        .postcondition([&] {
+            BOOST_CONTRACT_ASSERT(result * result <= x);
+            BOOST_CONTRACT_ASSERT((result + 1) * (result + 1) > x);
+        })
+    ;
+
+    return result = long(std::sqrt(double(x)));
+}
+
+int main() {
+    assert(lsqrt(4) == 2);
+    return 0;
+}
+//]
+