#include<stdio.h>

int main(){

FILE *file1, *file2;
long long element, maxim = 0, suma = 0, N;

file1 = fopen("operatii.in", "r");
file2 = fopen("operatii.out", "w");

fscanf(file1, "%lld", &N);

while(N){

    fscanf(file1, "%lld", &element);

    if(element){

        maxim = (element>maxim) ? element : maxim;

    }
    if(!element || N==1){

        suma += maxim;
        maxim = 0;

    }

    N--;
}

fprintf(file2, "%lld", suma);

return 0;
}