#include <cstdio>
#include <cstdint>
#include <algorithm>
#include <utility>
#include <vector>

int main() {
  size_t n;
  scanf("%zu", &n);

  std::vector<intmax_t> a(n+n);
  for (auto& ai: a) scanf("%jd", &ai);

  std::vector<intmax_t> left(n), right(n);
  for (size_t i = 0; i < n; ++i) {
    left[i] = a[i<<1] - a[i<<1|1];
    right[i] = -left[i];
  }

  {
    left.insert(left.begin(), 0);
    for (size_t i = 1; i <= n; ++i) left[i] += left[i-1];
    right.push_back(0);
    for (size_t i = n; i--;) right[i] += right[i+1];
  }

  intmax_t res = -1e15;
  for (size_t i = 0; i <= n; ++i) {
    // fprintf(stderr, "%jd?\n", left[i]+right[i]);
    res = std::max(res, left[i]+right[i]);
  }

  printf("%jd\n", res);
}