Excursie

#include <iostream>
using namespace std;

int main()
{
    int n;
    cin>>n;
    int A[n],B[n];
    for(int i=0;i<n;++i)
        cin>>A[i]>>B[i];
    int en,ea,nro,j;
    for(int i=0;i<n;++i)
    {
        j=i;
        en=A[j];
        ea=B[j];
        nro=0;
        while(ea>=en&&nro<n)
            ea-=en,++j,j%=n,ea+=B[j],en=A[j],++nro;
        if(nro==n)
        {
            cout<<i+1;
            return 0;
        }
    }
    cout<<-1;
    return 0;
}