diff --git a/src/8/20/hash.cpp b/src/8/20/hash.cpp
new file mode 100644
index 0000000..6837ca0
--- /dev/null
+++ b/src/8/20/hash.cpp
@@ -0,0 +1,36 @@
+#include <algorithm>
+#include <cstdint>
+#include <ios>
+#include <string>
+#include <vector>
+#include <iostream>
+
+using ull = uint64_t;
+
+template<ull P=47,ull maxsize=(ull)1e3>
+struct Hash{
+    ull hash{};
+    std::vector<ull> powp;
+    Hash(const std::string&s):powp(maxsize){
+        ull npp=P;
+        powp[0]=1;
+        powp[1]=npp;
+        for(ull i=2;i<maxsize;i++){
+            npp*=npp;
+            powp[i]=npp;
+        }
+        ull k=0;
+        for(auto it=s.rbegin();it!=s.rend();++it){
+            hash+=((*it)-'A'+1)*powp[k];
+        }
+    }
+    bool operator==(const Hash<P,maxsize>&o)const{
+        return hash==o.hash;
+    }
+};
+
+#define pv(v)do{std::cout<<std::boolalpha<<#v<<" :"<<(v)<<'\n';}while(0)
+
+int main(){
+    pv(Hash("aaaaaaaa")==Hash("aaaaaaa"));
+}   
\ No newline at end of file