#include <stdio.h>
#include <stdlib.h>
#include <string.h>

long long max(long long a, long long b) {
    return a > b ? a : b;
}

long long maxAlternatingSum(int* nums, int numsSize) {
    // buy: max sum when we can buy (add) next element
    // sell: max sum when we can sell (subtract) next element
    long long buy = 0, sell = 0;
    
    for (int i = 0; i < numsSize; i++) {
        // New buy state: either keep old buy, or sell then buy current
        long long newBuy = max(buy, sell + nums[i]);
        // New sell state: either keep old sell, or buy then sell current
        long long newSell = max(sell, buy - nums[i]);
        
        buy = newBuy;
        sell = newSell;
    }
    
    // We want the maximum, which is the buy state (ending with addition)
    return buy;
}

int main() {
    char line[10000];
    fgets(line, sizeof(line), stdin);
    
    int nums[100000];
    int count = 0;
    char* token = strtok(line, " \n");
    while (token != NULL) {
        nums[count++] = atoi(token);
        token = strtok(NULL, " \n");
    }
    
    printf("%lld\n", maxAlternatingSum(nums, count));
    return 0;
}