#include<iostream>
#include<string>
using namespace std;

int main(){

int a,b,c;

cin>>a;
cin>>b;
cin>>c;

int bb,ab,abc;
bb=b/10;
ab=a+bb;

for(int i=0;bb>i;++i){
    abc=ab+i*9;
    if(abc>c){
        ab+=i;
        cout<< ab-c;
    }
}


    
    
    
    
}