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

int a[1001], b[1001], startingPosition, s, n;
bool solutionExists = 0, isGood;

int main()
{
    cin >> n;
    for (int i = 0; i < n; ++i)
    {
        cin >> a[i] >> b[i];
    }
    for (int i = 0; i < n; ++i)
    {
        isGood = 1;
        s = 0;
        for (int j = i; j < n + i; ++j)
        {
            s += b[j % n] - a[j % n];
            if (s < 0) isGood = 0;
        }
        if (isGood) { solutionExists = 1; startingPosition = i; break; }
    }
    if (!solutionExists) cout << -1;
    else cout << startingPosition + 1;
    return 0;
}