#include <bits/stdc++.h>
using namespace std;
typedef long long int lli;
const int MAXN = 510;
const int MAXV = 1000000000;
const int MOD = 1000000007;
class SparseSegmentTree
{
public:
void create()
{
e.push_back( 0 );
d.push_back( 0 );
sum.push_back( 0 );
}
int getLeft(int node)
{
if( e[node] == 0 )
{
e[node] = ++cntNode;
create();
}
return e[node];
}
int getRight(int node)
{
if( d[node] == 0 )
{
d[node] = ++cntNode;
create();
}
return d[node];
}
void update(int node, int l, int r, int i, int v)
{
if( i < l || r < i ) return;
if( l == r )
{
sum[node] += v;
sum[node] %= MOD;
return;
}
int m = ( l + r )/2;
if( i <= m ) update( getLeft(node) , l , m , i , v );
else update( getRight(node) , m + 1 , r , i , v );
sum[node] = sum[ e[node] ] + sum[ d[node] ];
sum[node] %= MOD;
}
int query(int node, int l, int r, int i, int j)
{
if( node == 0 ) return 0;
if( j < l || r < i ) return 0;
if( i <= l && r <= j ) return sum[node];
int m = ( l + r )/2;
int sumLeft = query( e[node] , l , m , i , j );
int sumRight = query( d[node] , m + 1 , r , i , j );
return ( sumLeft + sumRight )%MOD;
}
SparseSegmentTree() : cntNode(1) { create(); create(); }
private:
int cntNode;
vector< int > e, d;
vector< int > sum;
};
int n;
SparseSegmentTree SEG;
int main()
{
scanf("%d",&n);
SEG.update( 1 , 0 , MAXV , 0 , 1 );
for(int i = 1 ; i <= n ; i++)
{
int l, r;
scanf("%d %d",&l,&r);
vector< int > aux;
for(int j = l ; j <= r ; j++)
aux.push_back( SEG.query( 1 , 0 , MAXV , 0 , j - 1 ) );
for(int j = 0 ; j < aux.size() ; j++)
SEG.update( 1 , 0 , MAXV , j + l , aux[j] );
}
printf("%d\n",SEG.query( 1 , 0 , MAXV , 1 , MAXV ));
}
