#include<cstdio>
int v[1000005],n,k,x,y,c,i,j;
long long t;
int main()
{
    freopen("gardieni.in","r",stdin),freopen("gardieni.out","w",stdout),scanf("%d%d",&n,&k);
    for(i=1;i<=n;++i)
        for(scanf("%d%d%d",&x,&y,&c),j=x;j<=y;++j)
            if(v[j]>c||!v[j])
                t+=c-v[j],v[j]=c;
    printf("%lld",t);
    return 0;
}