#include<iostream>
#include<cstdio>
#include<algorithm>
int n,m;
long long sum[400005], lazy[400005];
int f,x,y;
long long k;
void pushdown(int x, int L, int R){
    if (lazy[x] != -1){//把整个区间赋值为懒标记的值 
        int mid = (L + R) >> 1;
        lazy[x << 1] = lazy[x];
        lazy[x << 1 | 1] = lazy[x];//下放与更新 
        sum[x << 1] = lazy[x] * (mid - L + 1);
        sum[x << 1 | 1] = lazy[x] * (R - mid);
        lazy[x] = -1;
    }
    return;
}
void pushup(int x){
    sum[x] = sum[x << 1] + sum[x << 1 | 1];
    return;
}
void update(int x, int l, int r, int L, int R, long long d){
    if (L <= l && r <= R){//懒标记的新意义 
        lazy[x] =d;
        sum[x] = d * (r - l + 1);
        return;
    }
    int mid = (l + r) >> 1;
    pushdown(x, l, r);
    if (L <= mid) update(x << 1, l, mid, L, R, d);
    if (R > mid) update(x << 1 | 1, mid + 1, r, L, R, d);
    pushup(x);
}
long long query(int x, int l, int r, int L, int R){
    if (L <= l && r <= R){
        return sum[x];
    }
    int mid = (l + r) >> 1;
    pushdown(x, l, r);
    long long ans = 0;
    if (L <= mid) ans += query(x << 1, l, mid, L, R);
    if (R > mid) ans += query(x << 1 | 1, mid + 1, r, L, R);
    return ans;
}
int main(){
    scanf("%d%d",&n,&m);
    for(int i=1;i<=400005;++i)//因为是0和1两种状态，所以不能是0 
    lazy[i]=-1;
    for(int i=0;i<=n;++i){
        update(1, 0, n, i, i, 1);//种树？全赋值为一呗 
    }
    for(int i=1;i<=m;++i){
            scanf("%d%d",&x,&y);
            update(1, 0, n, x, y, 0);//砍树，全赋值为零呗 
    }
    printf("%lldn", query(1, 0, n, 0, n));
    return 0;
}