#include <cstdio>

FILE* in=fopen("stergeri.in","r");
FILE* out=fopen("stergeri.out","w");

void rec(int t, int &k)
{
    if(t==0)
        return;
    int a,b;
    fscanf(in,"%d%d",&a,&b);
    rec(t-1,k);
    if(a<=k)
        k+=b-a+1;
}

int main()
{
    int n,t,k;
    fscanf(in,"%d%d%d",&n,&t,&k);
    rec(t,k);
    fprintf(out,"%d",k);
    return 0;
}