C++ :

#include<bits/stdc++.h>
using namespace std;
int n,m,ans,a[200005],x,y,b[200005];
int ws(int x)
{
	int ans1=0;	
	if(x==0) ans1=1;
	while(x>0){
		ans1++;
		x/=10;
	}
	return ans1;
}
int main()
{	
	cin>>n>>m;
	while(m--)
	{
		cin>>x>>y;
		a[x]++,a[++y]--;
	}
	for(int i=1;i<=n;i++)
		b[i]=a[i]+b[i-1];
	for(int i=1;i<=n;i++)
		ans+=ws(b[i]);
	cout<<ans;

    return 0;
}