[bzoj1811] [Ioi2005]mea

 1 #include<cstdio>
 2 #include<iostream>
 3 #include<cstring>
 4 #define ll long long
 5 using namespace std;
 6 const int maxn=5002333;
 7 int i,j,k,n,m;
 8  
 9 int ra;char rx;
10 inline int read(){
11     rx=getchar(),ra=0;
12     while(rx<‘0‘||rx>‘9‘)rx=getchar();
13     while(rx>=‘0‘&&rx<=‘9‘)ra*=10,ra+=rx-48,rx=getchar();return ra;
14 }
15 int main(){
16     ll sm,mx,mn;int pre,now;
17     n=read();pre=mn=sm=read(),mx=-(1<<30);
18     for(i=2;i<=n&&mx<=mn;i++){
19         now=read();
20         if(i&1)sm+=now-pre,mn=min(mn,sm);else sm+=pre-now,mx=max(mx,sm);
21 //      printf("  %lld  %lld    sm:%lld\n",mx,mn,sm);
22         pre=now;
23     }
24     if(mx>mn)puts("0");else printf("%lld\n",mn-mx+1);
25 }