#include <iostream>

#include <map>

#include <string>

#include <functional>

template <typename Key, typename Value, typename F>

void update(std::map<Key, Value>& m, F foo) {

for (auto&& [key, value] : m ) value = foo(key);

}

int main() {

std::map<std::string, long long int> m {

{"a", 1},

{"b", 2},

{"c", 3}

};

update(m, [](std::string key) -> long long int {

return std::hash<std::string>{}(key);

});

for (auto&& [key, value] : m)

std::cout << key << ":" << value << std::endl;

}