#include <stdio.h>

int main(void){

    int N = 0;
    int dist = 0;
    int max_prev = 0;
    int max = 0;
    int tmp = 0;
    
    scanf("%d", &N);
    
    for(int i=0; i<N; i++){
        
        scanf("%d", &dist);
        
        if(max_prev + dist > max){
            tmp = max;
            max = max_prev + dist;
            max_prev = tmp;
            
        }else{
            max_prev = max;
        }
    }
    
    printf("%d\n", max);
    
    return 0;
    
    
}