How do I stop overflowing numbers in C?

510
* 5
* 9
+ 9
* 9932
* 1925
* 4
+ 918
* 7
* 9307
* 9
+ 96
* 1063
* 4
* 1380
* 100
+ 119
+ 8377
* 718
* 87
* 57
* 7548
* 52
+ 7227
+ 7
+ 1
+ 6204
+ 598
+ 48
+ 740
+ 4698
+ 4
* 81
+ 718
* 90
* 4
* 2065
+ 8741
* 244
+ 93
* 9
+ 8875
* 16
* 76
* 1
* 112
+ 1
+ 9
+ 4450
+ 8859
% 9602

 #include<stdio.h>
 #include<conio.h>
int main()
{
    int str[1];
    int i , j ,num1;
    char ch;
    scanf("%d",&str[0]);
    while (1)
    {
        ch=getche();
        scanf(" %d",&num1);
        if(ch=='+')
        {
            str[0]=str[0]+num1;
             printf("%d ",str[0]);
        }
        if(ch =='*')
        {
            str[0]=str[0]*num1;
            printf("%d ",str[0]);
        }
        if(ch =='%')
        {
            str[0]=str[0]%num1;
                break;
        }

    }

    return 0;
}