HDU 5055 Bob and math problem

#include <cstdio>

int t,n,a[10];

int main(){

    while(~scanf("%d",&n)){

        int flag=0;

        for(int i=0;i<10;i++)a[i]=0;

        for(int i=0;i<n;i++)scanf("%d",&t),a[t]++;

        if(n==1){printf("%d\n",t&1?t:-1);continue;}

        for(int i=1;i<10;i+=2)if(a[i]){flag=1;a[i]--;t=i;break;}

        if(flag==0){puts("-1");continue;}flag=0;

        for(int i=1;i<10;i++)if(a[i]>0)flag=1;

        if(flag==0){puts("-1");continue;}

        for(int i=9;i>=0;i--)while(a[i]>0)printf("%d",i),a[i]--;

        printf("%d\n",t);

    }return 0;

}

//注意n==1的情况