#include <algorithm>
#include <iostream>
#include <string>
#include <vector>
using namespace std;
 
int main() {
	std::vector<std::string> foo;
	foo.push_back("A");
	foo.push_back("B");
	std::string::size_type total = 0;
    std::accumulate(foo.begin(), foo.end(), total, 
                    [](std::string::size_type i, std::string const& s) { return i + s.size(); });
    cout << total << endl;
    std::string result;
    result.reserve(total);
    std::for_each(foo.begin(), foo.end(), 
                  [&](std::string const& s) { result += s; });
    cout << result << endl;
	return 0;
}

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