#include <iostream>
#include <map>
#include <iterator>
#include <algorithm>
using namespace std;
int main() {
map<int,int> m;
m[1] = 10;
m[2] = 20;
m[3] = 30;
auto target = 20;
auto f20 = std::find_if(std::begin(m), std::end(m), [&](const auto& p) {
return p.second == target;
});
cout << f20->first << " " << f20->second << endl;
return 0;
}
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