//Lib
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<cmath>
#include<ctime>
 
#include<iostream>
#include<algorithm>
#include<vector>
#include<string>
#include<queue>
#include<stack>
#include<set>
#include<map>
using namespace std;
//Macro
#define rep(i,a,b)  for(int i=a,tt=b;i<=tt;++i)
#define drep(i,a,b) for(int i=a,tt=b;i>=tt;--i)
#define erep(i,e,x) for(int i=x;i;i=e[i].next)
#define irep(i,x)   for(__typeof(x.begin()) i=x.begin();i!=x.end();i++)
#define read()  (strtol(ipos,&ipos,10))
#define sqr(x)  ((x)*(x))
#define pb  push_back
#define PS  system("pause");
typedef long long   ll;
typedef pair<int,int> pii;
const int oo=~0U>>1;
const double inf=1e100;
const double eps=1e-6;
string name="", in=".in", out=".out";
//Var
int f[30][30],n,len,ans;
void Work()
{
    memset(f,55,sizeof f);
    scanf("%d",&n);
    rep(i,1,n)f[i][i]=0;
    rep(i,1,n-1)
    {
        scanf("%d",&len);
        f[i][i+1]=f[i+1][i]=len;
    }
    scanf("%d",&len);f[n][1]=f[1][n]=len;
    rep(k,1,n)rep(i,1,n)rep(j,1,n)if(i!=j&&i!=k&&j!=k)f[i][j]=min(f[i][j],f[i][k]+f[k][j]);
    rep(i,1,n)rep(j,i+1,n)rep(k,j+1,n)rep(l,k+1,n)
        if(f[i][j]==f[k][l]&&f[i][l]==f[j][k])ans++;
    cout<<ans<<endl;
}
int main()
{
//  freopen((name+in).c_str(),"r",stdin);
//  freopen((name+out).c_str(),"w",stdout);
//  Init();
    Work();
    return 0;
}