Max difference.

#include <bits/stdc++.h> // header file includes every Standard library
using namespace std;

int main() {
    int N;
    cin >> N;

    vector<int> arr;


    while(N--){
        int temp;   cin >> temp;
        arr.push_back(temp);
    }

    multimap<int, int> uMap;
    for(int i=0; i<arr.size(); i++){
        uMap.insert(pair <int, int> (arr[i], i));
        //uMap[arr[i]] = i;
    }

    int answer = -1;
    int maxSoFar = -1;
    for (auto i = uMap.rbegin(); i != uMap.rend(); ++i) {
        answer = max(answer, maxSoFar - i->second);
        maxSoFar = max(maxSoFar, i->second);
    }

    cout << answer << endl;

    return 0;
}