hdu2444

#include <stdio.h>
#include <string.h>
#define  black 1
#define  white -1
int already[201];
int in[201];
int gr[201][201];
int n;
int v[201];
int pf,pe;

int dfs(int a,int color){
    v[a]=color;
    int i;
    int sign;
    for(i=1;i<=n;++i){
        if(i==a) continue;
        if(gr[a][i]&&v[i]==0){
            if((sign=dfs(i,-color))==-1) return -1;
        }else if(gr[a][i]&&v[i]==color){
            return -1;
        }
    }
    return 1;
}
int judge(){
    int i;
    int sign;
    memset(v,0,sizeof(v));
    for(i=1;i<=n;++i){
        if(0==v[i]){
            if((sign=dfs(i,black))==-1) return -1;
        }
    }
    return 1;
}

int find(int a){
    int i;
    for(i=1;i<=n;++i){
        if(v[i]==white&&gr[a][i]&&!in[i]){
            in[i]=1;
            if(already[i]==0||find(already[i])){
                already[i]=a;
                return 1;
            }
        }
    }
    return 0;
}
int main(){
    int m;
    int i,j;
    int res;
    while(~scanf("%d%d",&n,&m)){
        res=0;
        memset(gr,0,sizeof(gr));
        while(m--){
            scanf("%d%d",&i,&j);
            gr[i][j]=1;
            gr[j][i]=1;
        }
        if(judge()==-1){
            printf("No
");
            continue;
        }

        memset(already,0,sizeof(already));
        for(i=1;i<=n;++i){
            memset(in,0,sizeof(in));
            if(v[i]==black)
                if(find(i))
                    res++;
        }
        printf("%d
",res);
    }
    return 0;
}