Министерство правды

#include <iostream>
#include <string>
#include <map>
#include <set>
#include <algorithm>
#include <vector>
#include <stdio.h>
#include <cmath>
#include <math.h>
#include <queue>
#include <stack>
#include <climits>
#include <deque>
#include <ctime>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef unsigned int ui;

int main()
{
    string s;
    getline(cin, s);

    string y;
    string u = s;
    queue<pair<int, int>>next;
    ll last;
    cin >> y;
    ll i = -1;
    i = s.find(y);
    if (i == 4294967295)
        return cout << "I HAVE FAILED!!!", 0;
    next.push({ i, i + y.size()-1});
    last = i + y.size() - 1;
    while (cin >> y)
    {
        i = s.substr(last+2,s.size()-last-2).find(y);
        if (i == 4294967295)
            return cout << "I HAVE FAILED!!!", 0;
        else
            i += last + 2;
        next.push({ i, i+y.size()-1 });
        last = i + y.size() - 1;
    }

    for (int i = 0; i < s.size(); i++)
    {
        if (!next.empty())
            if (i >= next.front().first&&i <= next.front().second)
            {
                cout << s[i];
                if (i + 1 > next.front().second)
                    next.pop();
            }
            else
            {
                if (s[i] != ' ')
                    cout << "_";
                else
                    cout << s[i];
            }
        else
        {
            if (s[i] != ' ')
                cout << "_";
            else
                cout << s[i];
        }
    }
    system("pause");
    return 0;
}