Good Bye 2016 C. New Year and Rating（二分）

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Description

Every Codeforces user has rating, described with one integer, possibly negative or zero. Users are divided into two divisions. The first division is for users with rating 1900 or higher. Those with rating 1899 or lower belong to the second division. In every contest, according to one's performance, his or her rating changes by some value, possibly negative or zero.

Limak competed in n contests in the year 2016. He remembers that in the i-th contest he competed in the division di (i.e. he belonged to this division just before the start of this contest) and his rating changed by ci just after the contest. Note that negative ci denotes the loss of rating.

What is the maximum possible rating Limak can have right now, after all n contests? If his rating may be arbitrarily big, print "Infinity". If there is no scenario matching the given information, print "Impossible".

Input

The first line of the input contains a single integer n (1 ≤ n ≤ 200 000).

The i-th of next n lines contains two integers ci and di ( - 100 ≤ ci ≤ 100, 1 ≤ di ≤ 2), describing Limak's rating change after the i-th contest and his division during the i-th contest contest.

Output

If Limak's current rating can be arbitrarily big, print "Infinity" (without quotes). If the situation is impossible, print "Impossible" (without quotes). Otherwise print one integer, denoting the maximum possible value of Limak's current rating, i.e. rating after the ncontests.

Sample Input

3
-7 1
5 2
8 2

2
57 1
22 2

1
-5 1

4
27 2
13 1
-50 1
8 2

Sample Output

1907

Impossible

Infinity

1897

Note

In the first sample, the following scenario matches all information Limak remembers and has maximum possible final rating:

• Limak has rating 1901 and belongs to the division 1 in the first contest. His rating decreases by 7.
• With rating 1894 Limak is in the division 2. His rating increases by 5.
• Limak has rating 1899 and is still in the division 2. In the last contest of the year he gets  + 8 and ends the year with rating 1907.

In the second sample, it's impossible that Limak is in the division 1, his rating increases by 57 and after that Limak is in the division 2 in the second contest.

思路

题解:

二分查找出符合题意的值，判断最后判断二分出来的结果是不是正确的。

 

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#include<bits/stdc++.h> using namespace std; const int maxn = 200005; const int Left = -20000000; const int Right = 20001900; struct Node{     int val,type; }node[maxn]; int n;   bool OK(int x) {     for (int i = 0;i < n;i++)     {         if (node[i].type == 1)         {             if (x < 1900)    return true;             x += node[i].val;         }         else         {             if (x > 1899)    return false;             x += node[i].val;         }     }     return true; }   int main() {     //freopen("input.txt","r",stdin);     scanf("%d",&n);     for (int i = 0;i < n;i++)    scanf("%d%d",&node[i].val,&node[i].type);     int left = Left,right = Right + 300;     while (left < right - 1)     {         int mid = left + ((right-left)>>1);         if (OK(mid))         {             left = mid;         }         else         {             right = mid;         }     }     int val = left,sum = left;     for (int i = 0;i < n;i++)     {         if (node[i].type == 1)         {             if (sum < 1900)             {                 printf("Impossible\n");                 return 0;             }             else    sum += node[i].val;         }         else         {             if (sum > 1899)             {                 printf("Impossible\n");                 return 0;             }             else    sum += node[i].val;         }     }     if (val >= Right)    printf("Infinity\n");     else    printf("%d\n",sum);     return 0; }