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

int n, inSum, outSum;
int in[40], out[40];

int main(void) {
    scanf("%d", &n);

    for (int i = 0; i < n-1; ++i) {
        scanf("%d %d", &in[i], &out[i]);

        inSum += in[i];
        outSum += out[i];
    }

    if (inSum != outSum) printf("%d\n", abs(inSum - outSum));
    else printf("%d\n", inSum + 1);
}