#include <stdio.h>

int N, A[37], B[37];

int min(int x, int y) {
    return x < y ? x : y;
}

int max(int x, int y) {
    return x > y ? x : y;
}

int main() {
    scanf("%d", &N);
    int sa = 0;
    int sb = 0;
    for (int i = 1; i < N; i++) {
        scanf("%d %d", &A[i], &B[i]);
        sa += A[i];
        sb += B[i];
    }
    int ma = 0;
    int mb = 0;
    for (int i = 1; i < 37; i++) {
        ma = max(ma, B[i] - (sa - A[i]));
        mb = max(mb, A[i] - (sb - B[i]));
    }
    printf("%d\n", min(sb - ma, sa - mb) + 1);
    return 0;
}