Codeforces Problem - 617B Chocolate

http://www.codeforces.com/problemset/problem/617/B

B. Chocolate

time limit per test
1 second

memory limit per test
256 megabytes

input
standard input

output
standard output

Bob loves everything sweet. His favorite chocolate bar consists of pieces, each piece may contain a nut. Bob wants to break the bar of chocolate into multiple pieces so that each part would contain exactly one
nut and any break line goes between two adjacent pieces.

You are asked to calculate the number of ways he can do it. Two ways to break chocolate are considered distinct if one of them contains a break between some two adjacent pieces and the other one doesn't.

Please note, that if Bob doesn't make any breaks, all the bar will form one piece and it still has to have exactly one nut.

Input

The first line of the input contains integer n (1 ≤ n ≤ 100) —
the number of pieces in the chocolate bar.

The second line contains n integers ai (0 ≤ ai ≤ 1),
where 0 represents a piece without the nut and 1 stands
for a piece with the nut.

Output

Print the number of ways to break the chocolate into multiple parts so that each part would contain exactly one nut.

Examples

input

3
0 1 0

output

1

input

5
1 0 1 0 1

output

4

Note

In the first sample there is exactly one nut, so the number of ways equals 1 — Bob shouldn't make any breaks.

In the second sample you can break the bar in four ways:

10|10|1
1|010|1
10|1|01
1|01|01
我的思路就是：

有n个1就应该放n-1个bar

两个1距离多少，放当前这个bar的时候就有几个地方放，用乘法原理

#include <stdio.h>
int arr[1001];
#define LL __int64int main()
{
int n;
while(~scanf("%d",&n))
{
int cnt=0;
for(int i=1;i<=n;++i)
{
scanf("%d",arr+i);
if(arr[i]) cnt++;
}
if(cnt==0)
{
printf("0\n");
continue;
}
if(cnt==1)
{
printf("1\n");
continue;
}
LL ans=1;
int j;
for(int i=1;i<=n;++i)
{
if(arr[i])
{
j=i;
break;
}
}
int t=j;
for(int i=1;i<=n;++i)
{
if(i==t) continue;
if(arr[i])
{
ans*=i-j;
j=i;
}
}
printf("%I64d\n",ans);
}
return 0;
}