[Blue Bridge Cup 2015 Finals] The puzzle of points

#include<stdio.h>

int main(){
    
    
	int a,b,c;
	for(a=1;a<500;a++){
    
    
		for(b=1;b<500;b++){
    
    
			for(c=1;c<500;c++){
    
    
				if(3*a+7*b+c==315&&4*a+10*b+c==420){
    
    
					printf("%d\n",a+b+c);
					return 0;
				}
			}
		}
	}
}