POJ 2562 Primary Arithmetic

#include <iostream>
#include <cstdio>
#include <cstdio>
#define REP(i, s, n) for(int i = s; i <= n; i ++)
#define REP_(i, s, n) for(int i = n; i >= s; i --)
#define MAX_N 10 + 5

using namespace std;

char a[MAX_N], b[MAX_N];
int int_a[MAX_N], int_b[MAX_N], la, lb;

int main(){
    while(scanf("%s%s", a + 1, b + 1) != EOF){
        if(a[1] == ‘0‘ && b[1] == ‘0‘) break;
        memset(int_a, 0, sizeof(int_a)); memset(int_b, 0, sizeof(int_b));
        la = strlen(a + 1), lb = strlen(b + 1);
        REP(i, 1, la) int_a[la - i + 1] = a[i] - ‘0‘;
        REP(i, 1, lb) int_b[lb - i + 1] = b[i] - ‘0‘;
            
        int i = 1, x = 0, res = 0;
        while(i <= la || i <= lb){
            x = int_a[i] + int_b[i] + x;
            x /= 10;
            if(x != 0) res ++;
            i ++;
        }
        
        if(res == 0) printf("No carry operation.\n");
        else if(res == 1) printf("%d carry operation.\n", res);
        else printf("%d carry operations.\n", res);
    }
    return 0;
}