for this problem CodeChef: Practical coding for everyone i am getting an wrong answer but my test cases and run are showing successfully executed please help me find out the error.
here is code 
#include<bits/stdc++.h>
using namespace std;
#define ll long long int
int main()
{
ll t;
cin>>t;
while(t–)
{
ll n,q,i;
cin>>n>>q;
ll f[100000],d[100000];
for(i=0;i<q;i++)
{
cin>>f[i]>>d[i];
}
ll g,s=0;
for(i=1;i<q;i++)
{
g=d[i]-f[i];
if(g<0)
{
g=g*-1;
}
s=s+g;
}
ll h;
for(i=0;i<q-1;i++)
{
h=d[i]-f[i+1];
if(h<0)
{
h=h*-1;
}
s=s+h;
}
cout<<s+d[0]<<endl;
}
return 0;
}
please mark out the error
thank in advance