//9:45 50pt #include<bits/stdc++.h> using namespace std; #define int long long const int MAXN=100010,Mod=1000000007; int n,m,ans,p[MAXN],q[MAXN],L[MAXN],R[MAXN]; void fz(int l,int r){ if(l>r)return; if(l==r){ if(q[l]==p[l])ans++; return; } int mid=(l+r)>>1; //cout<<l<<" "<<r<<" "<<mid<<endl; int pm=Mod,qm=-1; for(int i=mid;i>=l;i--){ pm=min(pm,p[i]); L[i]=(pm>=i); } for(int i=mid;i<=r;i++){ qm=max(qm,q[i]); R[i]=(qm<=i); } R[mid-1]=0; // for(int i=l;i<=r;i++){ // cout<<((i<mid)?L[i]:R[i])<<" "; // } // cout<<endl; int Q=q[mid]; for(int i=mid;i<=r;i++)R[i]+=R[i-1]; // for(int i=l;i<=r;i++){ // cout<<((i<=mid)?L[i]:R[i])<<" "; // } // cout<<endl; for(int i=mid,j=mid;i>=l;Q=max(q[i],Q),i--){ while(i>=l&&!L[i]){ Q=max(q[i],Q); i--; } if(i<l)break; while(j<=r&&p[j]>=i)j++; // cout<<" "<<i<<" "<<j<<" "<<Q<<endl; ans+=R[j-1]-R[Q-1]; // cout<<"ans+="<<R[j-1]-R[Q-1]<<endl; } fz(l,mid-1); fz(mid+1,r); } signed main(){ freopen("vis.in","r",stdin); // freopen("vis.out","w",stdout); scanf("%lld%lld",&n,&m); for(int i=1;i<=n;i++)q[i]=p[i]=i; for(int i=1;i<=m;i++){ int u,v; scanf("%lld%lld",&u,&v); p[u]=(p[u])?min(p[u],v):v; q[u]=max(q[u],v); } // for(int i=1;i<=n;i++)cout<<p[i]<<" "<<q[i]<<endl; fz(1,n); printf("%lld",ans); return 0; }