#include <stdio.h>

int main() {
    int n;
    scanf("%d", &n);
    int dp[n + 1];
    int cost[n];
    for (int i = 0; i < n; i++) {
        scanf("%d", &cost[i]);
    }
    dp[0] = 0;
    dp[1] = 0;
    for (int j = 2; j <= n; j++) {
        dp[j] = dp[j - 1] + cost[j - 1] < dp[j - 2] + cost[j - 2] ? dp[j - 1] + cost[j -
                1] : dp[j - 2] + cost[j - 2];
    }
    printf("%d",dp[n]);
    return 0;
}