//No.2681 ゲームセンターの両替
#include <stdio.h>

int judge(int, int);
int change(int, int);

int main(void){
    int C, Y;
    scanf("%d %d", &C, &Y);

    switch(judge(C, Y)){
        case 1: printf("can't exchange\n");
                break;
        case 2: printf("no exchange\n");
                break;
        case 3: printf("%d\n", change(C, Y));
                break;           
    }

    return 0;
}

int judge(int C, int Y){
    if(C == 0){
        return 2;
    }else if(Y < 100 * C){
        return 1;
    }else if((Y % 1000) / 100 < C){
        return 3;
    }else{
        int j = (Y % 1000) / 100;
        if(j == 5 || j == 0){
            return 3;
        }else if(j >= 5){
            int i = j - 5;
            if(i >= C){
                return 2;
            }else{
                return 3;
            }
        }else{
            if(j >= C){
                return 2;
            }else{
                return 3;
            }
        }
    }
}

int change(int C, int Y){
    int cnt = 0;
    Y = Y - 100 * C;
    cnt += C;
    int num = Y / 500;
    Y = Y - 500 * num;
    cnt += Y / 100;

    return cnt;
}