/* ***********************************************
Author        :devil
************************************************ */
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <stack>
#include <map>
#include <unordered_map>
#include <string>
#include <time.h>
#include <cmath>
#include <stdlib.h>
#define LL long long
#define rep(i,a,b) for(int i=a;i<=b;i++)
#define dep(i,a,b) for(int i=a;i>=b;i--)
#define ou(a) printf("%d\n",a)
#define pb push_back
#define pii pair<int,int>
#define mkp make_pair
#define IN freopen("in.txt","r",stdin);
#define OUT freopen("out.txt","w",stdout);
using namespace std;
const int inf=0x3f3f3f3f;
const int mod=1e9+7;
const int N=1e2+10;
int n,ans,ans2;
pii a[N],b[N];
bool ok(pii x,pii y,pii z)
{
    if(x>z) swap(x,z);
    return x<y&&y<z;
}
int main()
{
    scanf("%d",&n);
    for(int i=1;i<=n;i++) scanf("%d%d",&a[i].first,&b[i].first),b[i].first+=a[i].first,a[i].second=-i,b[i].second=-i;
    for(int i=1;i<=n;i++)
        for(int j=1;j<=n;j++)
        {
            int p=ok(a[i],a[j],b[i])+ok(a[j],b[i],b[j]);
            if(p==2) ans+=2;else ans2+=p;
        }
    printf("%d\n",ans+ans2/2);
    return 0;
}