#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#define MAX(A, B) (A > B ? A : B)


int max_sum(int, int*);

int main(){
    FILE *filePointer;
    FILE *filePointer_out;
    int *array;
    int n, i = 0;

    filePointer = fopen("input.txt", "r");
    if (filePointer){
        fscanf(filePointer, "%d", &n);
        array = (int*)malloc(sizeof(int) * n);
        while (!feof(filePointer)){
            fscanf(filePointer, "%d", &array[i]);
            i++;
        }
    }
    else{
        printf("File txt not found...\n");
    }
    filePointer_out = fopen("output.txt", "w");
    if (filePointer_out){
        fprintf(filePointer_out, "%d", max_sum(n, array));
    }
    else{
        printf("File txt out not found...\n");
    }
}

int max_sum(int n, int* D_array){
    bool odd;
    int i, sum1 = 0, sum2 = 0;
    odd = false;

    if (n%2 != 0)
        odd = true;

    if (odd){
        for (i = 1; i < n; i += 2){
            sum1 += D_array[i];
        }
        return sum1;
    }
    else{
        for(i = 0; i < n; i+= 2){
            sum1 += D_array[i];
        }
        for(i = 1; i < n; i += 2){
            sum2 += D_array[i];
        }

        return MAX(sum1, sum2);

    }
}