#include <stdio.h>
#include <stdbool.h>

int max;

int manpuku( int *s, int num, int N );

int main()
{
        int N;
        int s[1000];
        scanf( "%d\n", &N );
        for( int i = 0; i < N -1; i++ ) {
                scanf( "%d ", s + i );
        }
        scanf( "%d\n", s + N -1 );

        printf("%d\n", manpuku( s, 0, N ) );
        return 0;
}

int manpuku( int *s, int num, int N )
{
        int tmp1, tmp2, tmp3, tmp4;
        int a, b;
        tmp1 = tmp2 = tmp3 = tmp4 = a = b = 0;

        if( num >= N ) {
                return 0;
        }

        tmp1 = s[num] + manpuku( s, num+2, N );
        tmp2 = s[num] + manpuku( s, num+3, N );
        tmp3 =          manpuku( s, num+1, N );
        tmp4 =          manpuku( s, num+2, N );

        a = tmp1 < tmp2 ? tmp2 : tmp1;
        b = tmp3 < tmp4 ? tmp4 : tmp3;
        return a  < b ? b : a;

}