47构造数
ac代码
#includeusing namespace std;typedef long long ll;const int N = 1000010;bool flag = false;int ii,jj;int main(){ll x;cin>>x;for(ll i = x/7;i>=0;i--){if((x- 7*i) % 4==0){flag = true;int j = (x-7*i )/ 4;ii =i,jj = j;for(ll j=0;j<jj;j++) cout<<"4";for(ll i =0;i<ii;i++) cout<<"7";return 0;}} cout<<"-1";return 0;}
