diff --git a/divide_and_conquer/karatsuba_algorithm_for_fast_multiplication.cpp b/divide_and_conquer/karatsuba_algorithm_for_fast_multiplication.cpp
index 3fa5c0c76..31ac8d84c 100644
--- a/divide_and_conquer/karatsuba_algorithm_for_fast_multiplication.cpp
+++ b/divide_and_conquer/karatsuba_algorithm_for_fast_multiplication.cpp
@@ -59,7 +59,7 @@ std::string addStrings( std::string first, std::string second )
         int64_t secondBit = second.at(i) - '0';
  
         int64_t sum = (firstBit ^ secondBit ^ carry)+'0'; // sum of 3 bits
-        sum = to_string(sum);
+        sum = std::to_string(sum);
         sum += result;
         result = sum;