#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int N=200050;
int n,m,a[N],b[N],c[N];
int heap[N],tsz;
void Push(int x)
{
++tsz;int i;
for(i=tsz;i>1 && b[x]>b[heap[i>>1]];i>>=1) heap[i]=heap[i>>1];
heap[i]=x;
}
void Pop()
{
int tmp=heap[tsz--],i,j;
for(i=1;i*2<=tsz;i=j)
{
j=i*2;
if(j!=tsz && b[heap[j+1]]>b[heap[j]]) j++;
if(b[heap[j]]>b[tmp]) heap[i]=heap[j];
else break;
}
heap[i]=tmp;
}
ll sum[N],need[N],add[N],ost[N];
vector<int> ids[N];
bool Check(ll mid, int pos, ll flip)
{
for(int i=1;i<=n;i++) add[i]=0;
for(int i=1;i<pos;i++) need[i]=(sum[i]+flip-mid+1)/2;
need[pos]=flip;
tsz=0;
ll done=0;
for(int i=1;i<=pos;i++)
{
for(int j:ids[i]) if(a[j]<=pos && pos<b[j]) Push(j),ost[j]=c[j];
while(tsz && done<need[i])
{
int j=heap[1];
ll work=min(ost[j],need[i]-done);
done+=work;
ost[j]-=work;
add[1]+=work;
add[a[j]]-=2*work;
add[b[j]]+=2*work;
if(!ost[j]) Pop();
}
if(done<need[i]) return 0;
}
for(int i=1;i<=n;i++)
{
add[i]+=add[i-1];
if(add[i]+sum[i]>mid) return 0;
}
return 1;
}
int main()
{
scanf("%i %i",&n,&m);
for(int i=1;i<=m;i++)
{
scanf("%i %i %i",&a[i],&b[i],&c[i]);
if(a[i]>b[i]) swap(a[i],b[i]);
sum[a[i]]+=c[i];
sum[b[i]]-=c[i];
ids[a[i]].push_back(i);
}
int fir=0,las=0;
for(int i=1;i<=n;i++)
{
sum[i]+=sum[i-1];
if(sum[i]>sum[fir]) fir=i;
if(sum[i]==sum[fir]) las=i;
}
ll top=sum[fir],bot=0,mid,ans=top;
while(top>=bot)
{
mid=top+bot>>1;
if(Check(mid,fir,sum[fir]-mid)||Check(mid,fir,sum[fir]-mid+1)
||Check(mid,las,sum[las]-mid)||Check(mid,las,sum[las]-mid+1)) ans=mid,top=mid-1;
else bot=mid+1;
}
printf("%lld\n",ans);
return 0;
}
