不说了，直接贴代码
#include<cstdio>
#include<queue>
#include<cstring>
#define MAXN 100
#define MAXM 10000
using namespace std;
struct edge{
	int t,l,next;
}e[MAXM];
int used,h[MAXN],s,t,dis[MAXN],cnt[MAXN],tf,tt,tl,n,m;
bool v[MAXN];
void addedge(int f,int t,int l){//{{{
	e[used].t=t;
	e[used].l=l;
	e[used].next=h[f];
	h[f]=used;
	used++;
}//}}}
bool spfa(int s){//{{{
	queue<int>q;
	q.push(s);
	memset(cnt,0,sizeof(cnt));
	memset(dis,0x3f,sizeof(dis));
	memset(v,0,sizeof(v));
	cnt[s]=1,dis[s]=0,v[s]=true;
	while(q.size()){
		int tmp=q.front();
		q.pop();
		v[tmp]=false;
		for(int i=h[tmp];i!=-1;i=e[i].next)
			if(dis[e[i].t]>dis[tmp]+e[i].l){
				dis[e[i].t]=dis[tmp]+e[i].l;
				if(!v[e[i].t]){
					q.push(e[i].t);
					v[e[i].t]=true;
					cnt[e[i].t]++;
				}
				if(cnt[e[i].t]>n)return false;
			}
	}
	return true;
}//}}}
int main()
{
	scanf("%d%d",&n,&m);
	memset(h,-1,sizeof(h));
	addedge(1,2,n);
	addedge(2,3,m);
	spfa(1);
	printf("%d",dis[3]);
	return 0;
}