#include<iostream>
#include<vector>
#include<utility>
#include<sstream>

using namespace std;
using Pairs = vector<pair<int, int>>;

Pairs foo(const vector<int>& v) {
    Pairs pairs;
    int first = v[0];
    int second = v[0], k = 0;
    for (size_t i = 1; i < v.size(); ++i) {
        if (second < v[i]) {
            second = v[i];
            ++k;
        }
        else {
            if (k != 0) {
                pairs.push_back({ first, second });
                first = v[i];
                second = v[i];
                k = 0;
            }
            else {
                first = v[i];
                second = v[i];
            }
        }
        if (i == v.size() - 1) {
            if (second != 0)
                pairs.push_back({ first, second });
        }
    }
    return pairs;
}

ostream& operator<<(ostream& stream, const Pairs& pairs) {
    for (const auto& item : pairs) {
        stream << item.first << ' ' << item.second << endl;
    }
    return stream;
}

int main()
{
    vector<int> v = { 2,1,2,4,3,2,3,5 };
    cout << foo(v);
}