Please correct the language of c.

#include<string.h>
#include<stdio.h>
#include<stdlib.h>

int main(void)
{
    char str1[10];
    char str2[10];
    char str3[10];

    int num1, res;
        printf("0P #1 : ");
        scanf("%s", str1);
    while (str1[0] != '0')
    {

        printf("OPER : ");
        scanf("%s", str2);
        printf("OP #2 : ");
        scanf("%s", str3);
        if (str2[0] == '@')
        {
            strcat(str1, str3);
            num1 = atoi(str1);
            res = num1 + 1;
            printf("result : %d\n", res);
        }
        else
        {
            strcat(str3, str1);
            num1 = atoi(str3);
            res = num1 - 1;
            printf("result : %d\n", res);
        }
    }

    return 0;
}