#define maxn 20020#include <cstdlib>#include <stdio.h>#include <algorithm>#include <string.h>#include <iostream>#include <vector>#include <queue>using namespace std;struct Tdata{ int oil, city; };struct cmp{bool operator()(const Tdata &a,const Tdata &b){return a.oil > b.oil;}};bool used[maxn];priority_queue<Tdata, vector<Tdata>, cmp> cnt;int n;int dis[maxn], oil[maxn];bool init(){if (scanf("%d", &n) == EOF) return false;for (int i=0; i<n; i++) {scanf("%d%d", &oil[i], &dis[i]);dis[i+n] = dis[i], oil[i+n] = oil[i];}return true;}void solve(){while (!cnt.empty()) cnt.pop();Tdata d; d.oil = d.city = 0;cnt.push(d);;int now=oil[0];memset(used, 0, sizeof used);int ret = -1;for (int i=1; i<2*n; i++){now-=dis[i-1]; while (!cnt.empty()) {if (now+cnt.top().oil < 0){used[cnt.top().city] = true;cnt.pop();}else break;}now+=oil[i];if (i<n) {d.oil = oil[i]-now, d.city = i;cnt.push(d);}else if (!used[i-n]) {printf("%dn", i-n);return;}}printf("impossiblen");}int main(int argc, char** argv) {while (init()) solve();return 0;}
