#include <bits/stdc++.h>
using namespace std;

int countPairs(const vector<int>& projectCosts, int target) {
    // Using an unordered set to keep track of visited numbers
    unordered_set<int> visited;
    int count = 0;

    // Iterate through each number in the list
    for (int cost : projectCosts) {
        // Check if there exists a number with the required difference
        if (visited.count(cost + target)) {
            count++;
        }
        if (visited.count(cost - target)) {
            count++;
        }
        // Add the current number to the visited set
        visited.insert(cost);
    }

    return count;
}

int main() {
    vector<int> projectCosts = {1, 3, 5};
    int target = 2;
    
    int result = countPairs(projectCosts, target);
    cout << result << endl; // Output should be 2

    return 0;
}