struct gasStation {
    int gas;
    int next;
};

int main() {
    int N;
    cin >> N;
    queue <struct gasStation> route;
    for (int i = 0; i < N; i++) {
        struct gasStation st;
        cin >> st.gas >> st.next;
        route.push(st);
    }
    int start = 0, passed = 0,  gas = 0;
    while (passed < N) {
        struct gasStation st = route.front();
        gas += st.gas;
        route.pop();

        if (gas >= st.next) {
            passed += 1;
            gas -= st.next;
        } else {
            start += passed + 1;
            passed = 0; gas = 0;
        }
        route.push(st);
    }
    cout << start << endl;
    
    return 0;
}