#include <stdio.h>

int main() {
    int y,m,d=0;
    scanf("%4d %d %2d",&y,&m,&d);
    int y1,m1,d1=0;
    scanf("%4d %d %2d",&y1,&m1,&d1);
    if(y1>y){
        printf("yes\n");
    }
    else if(y1<y){
        printf("no\n");
    }
    else {
        if(y1>y){
            printf("yes\n");
        }
        else if(y1<y){
            printf("no\n");
        }
        else {
            if(d1>=d){
                printf("yes\n");
            }
            else 
                printf("no\n");
        }
    }
    return 0;
}

嵌套判断