#include <iostream>
#include <algorithm>
const int MAXN = 1e5;
const long long INFTY = 1e18;
const int LEAVES = 1 << 17;
const int TSIZE = LEAVES << 1;
int height[MAXN], sails[MAXN];
int order[MAXN];
long long maxAdded[TSIZE];
long long lazy[TSIZE];
void setup()
{
for (int u = LEAVES; u > 0; u /= 2)
maxAdded[u] = INFTY;
}
void push(int node)
{
if (node < LEAVES)
{
lazy[node * 2] += lazy[node];
lazy[node * 2 + 1] += lazy[node];
}
maxAdded[node] += lazy[node];
lazy[node] = 0;
}
void add(int node, int left, int right, int reqLeft, int reqRight)
{
push(node);
if (reqLeft <= left && right <= reqRight)
{
lazy[node] = 1;
push(node);
}
else if (reqLeft < right && left < reqRight)
{
add(node * 2, left, (left + right) / 2, reqLeft, reqRight);
add(node * 2 + 1, (left + right) / 2, right, reqLeft, reqRight);
maxAdded[node] = std::max(maxAdded[node * 2], maxAdded[node * 2 + 1]);
}
}
long long read(int node, int left, int right, int leaf)
{
push(node);
if (right - left == 1)
return maxAdded[node];
int middle = (left + right) / 2;
if (leaf < middle)
return read(node * 2, left, middle, leaf);
return read(node * 2 + 1, middle, right, leaf);
}
int leftmost(int node, int left, int right, long long val)
{
push(node);
if (maxAdded[node] <= val)
return -1;
if (right - left == 1)
return right;
int first = leftmost(node * 2 + 1, (left + right) / 2, right, val);
if (first == -1)
return leftmost(node * 2, left, (left + right) / 2, val);
return first;
}
int main()
{
std::ios::sync_with_stdio(false);
std::cout.tie(nullptr);
std::cin.tie(nullptr);
int masts; std::cin >> masts;
for (int iMast = 0; iMast < masts; iMast++)
{
std::cin >> height[iMast] >> sails[iMast];
height[iMast]++;
order[iMast] = iMast;
}
std::sort(order, order + masts, [](int a, int b) { return (height[a] < height[b]); });
setup();
for (int iMast = 0; iMast < masts; iMast++)
{
int mast = order[iMast];
long long max = read(1, 0, LEAVES, height[mast] - sails[mast]);
int left = leftmost(1, 0, LEAVES, max);
int right = std::min(height[mast], leftmost(1, 0, LEAVES, max - 1));
add(1, 0, LEAVES, right, height[mast]);
add(1, 0, LEAVES, left, left + sails[mast] - height[mast] + right);
}
long long ans = 0;
for (int iNode = 1; iNode < TSIZE; iNode++)
{
push(iNode);
if (iNode > LEAVES && maxAdded[iNode] > 0)
ans += maxAdded[iNode] * (maxAdded[iNode] - 1) / 2;
}
std::cout << ans << '\n';
return 0;
}
