/* Mos Craciun si prietenii sai*/

#include <cstdio>
#define ll long long
const int maxn = 100005;

using namespace std;

int i , j , k , n , A[maxn], act , cnt;
ll int sol;

int main() {
    freopen("numarare.in","r",stdin);
    freopen("numarare.out","w",stdout);

    scanf("%d",&n);
    for( i = 1 ; i <= n ; ++i )
        scanf("%d",&A[i]);


    for( k = 1 ; k <= n - 1 ; ++k) {
        act = A[k] + A[k + 1];
        cnt = 0;
        for( i = k , j = k + 1; i >= 1 && j <= n && ( A[i] + A[j] ) == act ; --i , ++j)
            ++cnt;
        sol += cnt;
        }

    printf("%lld\n",sol);

    return 0;
}