#include <stdio.h>
#define MAXN 292
#define MOD 1000000007
int N, M, R;
int A[MAXN], B[MAXN];
long long All=1;
void INPUT() {
scanf("%d %d", &N, &M);
for(int i=1; i<=N; i++) {
scanf("%d %d", &A[i], &B[i]);
All*=(long long)(B[i]-A[i]+1);
All%=MOD;
}
scanf("%d", &R);
}
long long Dy[2][MAXN][3];
void PROCESS() {
long long Ans=All;
for(int p=0; p<=M; p++) {
for(int t0=0; t0<2; t0++)
for(int t1=0; t1<=N; t1++)
for(int t2=0; t2<=N; t2++)
Dy[t0][t1][t2]=0;
Dy[0][0][0]=1;
for(int i=1; i<=N; i++) {
int over, same, under;
if(A[i]<=p && p<=B[i]) over=B[i]-p;
else if(p<A[i]) over=B[i]-A[i]+1;
else over=0;
if(A[i]<=p && p<=B[i]) under=p-A[i];
else if(B[i]<p) under=B[i]-A[i]+1;
else under=0;
if(A[i]<=p && p<=B[i]) same=1;
else same=0;
for(int j=0; j<=N; j++) {
for(int k=0; k<=1; k++) {
Dy[i%2][j][k]=Dy[1-i%2][j][k]*(long long) under;
Dy[i%2][j][k]%=MOD;
}
}
for(int j=0; j<=N; j++) {
for(int k=0; k<=1; k++) {
Dy[i%2][j+1][k]+=Dy[1-i%2][j][k]*(long long)over;
Dy[i%2][j+1][k]%=MOD;
Dy[i%2][j][k+1]+=Dy[1-i%2][j][k]*(long long)same;
Dy[i%2][j][k+1]%=MOD;
}
}
}
Ans+=(MOD-Dy[N%2][R-1][1]);
Ans%=MOD;
}
printf("%lld\n", Ans);
}
int main() {
// freopen("input", "r", stdin);
INPUT();
PROCESS();
}
