XUT 1245

 1 #include <stdio.h>
 2 #include <string.h>
 3 #define inf 0x3f3f3f3f
 4 int main()
 5 {
 6     int m,n,a,b,c,falg;
 7     int dis[100005];
 8     long long ans;
 9     while(~scanf("%d%d",&m,&n))
10     {
11         ans = 0;
12         falg = 1;
13         memset(dis,inf,sizeof(dis));
14         for(int i = 1 ; i <= n ; i++ )
15         {
16             scanf("%d%d%d",&a,&b,&c);
17             if(b==a+1&&c<dis[a]) dis[a] = c;
18         }
19         for(int i = 1 ; i < m ; i++)
20         {
21             if(dis[i]==inf)
22             {
23                 falg = 0;
24                 break;
25             }
26             ans+=dis[i];
27         }
28         if(falg)printf("%lld\n",ans);
29         else printf("-1\n");
30     }
31 }