/*
_.-- ,.--.
.' .' /
@ |'..--------._
/ \._/ '.
/ .-.- \
( / \ \
\\ '. | #
\\ \ -. /
:\ | )._____.' \
" | / \ | \ )
| |./' :__ \.-'
'--'
*/
#include<bits/stdc++.h>
#define ll long long
#define llll pair<ll,ll>
#define ii pair<int,int>
#define fi first
#define se second
#define FOR(i,l,r) for(int i=l;i<=r;i++)
#define FOD(i,r,l) for(int i=r;i>=l;i--)
#define ull unsigned long long
#define iii pair<int,ii>
#define iv pair<pii,ii>
#define db double
#define ld long double
#define pb push_back
#define tdk "kfph"
using namespace std;
const int dx[] = {1, -1, 0, 0};
const int dy[] = {0, 0, -1, 1};
const int dxx[] = {1, 1, -1, -1, 2, 2, -2, -2};
const int dyy[] = {2, -2, 2, -2, 1, -1, 1, -1};
const ll INF=1e18;
const int N=1000;
const int mod=1e9+7;
int add(int a,int b)
{
return (a+b)%mod;
}
int mul(int a,int b)
{
return 1ll*a*b%mod;
}
int sub(int a,int b)
{
return ((a-b)%mod+mod)%mod;
}
namespace fenwick
{
int ft[N*4];
void init()
{
memset(ft,0,sizeof ft);
}
void update(int u,int val)
{
while(u<N*4)
{
ft[u]=add(ft[u],val);
u+=u&-u;
}
}
int get(int u)
{
int ret=0;
while(u>0)
{
ret=add(ret,ft[u]);
u-=u&-u;
}
return ret;
}
}
using namespace fenwick;
int dp[N][N*4],n,a[N],b[N],ans=0;
vector<int> val;
void kfph()
{
cin >> n;
for(int i=1;i<=n;i++)
{
cin >> a[i] >> b[i];
val.pb(a[i]);
val.pb(b[i]);
val.pb(a[i]-1);
val.pb(b[i]-1);
}
val.pb(0);
sort(val.begin(),val.end());
val.erase(unique(val.begin(),val.end()),val.end());
init();
update(1,1);
for(int i=1;i<=n;i++)
{
a[i]=lower_bound(val.begin(),val.end(),a[i])-val.begin()+1;
b[i]=lower_bound(val.begin(),val.end(),b[i])-val.begin()+1;
// cout << a[i] << ' ' << b[i] << '\n';
}
for(int i=1;i<=n;i++)
{
// cout << dp[i][1] << '\n';
dp[i][a[i]]=get(a[i]-1);
for(int j=a[i]+1;j<=b[i];j++)
{
dp[i][j]=mul(sub(val[j-1],val[j-2]),get(j-1));
}
for(int j=a[i];j<=b[i];j++)
{
update(j,dp[i][j]);
}
}
for(int i=1;i<=n;i++)
{
// cout << dp[i][1] << ' ';
for(int j=2;j<=val.size();j++)
{
// cout << dp[i][j] << " \n"[j==val.size()];
ans=add(ans,dp[i][j]);
}
}
cout << ans;
}
int main()
{
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
if(fopen(tdk".inp","r"))
{
freopen(tdk".inp","r",stdin);
freopen(tdk".out","w",stdout);
}
int t=1;
//cin >> t;
while(t--)
{
kfph();
}
return 0;
}
