C :

#include<stdio.h>
#include<string.h>
main()
{
	char ch1[60], ch2[60];
	int result;
	while(scanf("%s %s",&ch1,&ch2)!=EOF)
	{
		result=0;
	for(int i=0;i<strlen(ch1);i++)
	for(int j=0;j<strlen(ch2);j++)
	result+=(ch1[i]-48)*(ch2[j]-48);
	printf("%d\n",result);
	}
}

C++ :

#include <stdio.h> 
#include <string.h> 
int suma,sumb,sum; 
char a[40],b[40]; 
int numa[40],numb[40]; 
int main() 
{ 
    int lengtha ,lengthb,i,temp,j;  
    while(scanf("%s %s",a,b)!=EOF) 
    { 
        suma=0; 
        sumb=0; 
    lengtha = strlen(a); 
    lengthb = strlen(b); 
    for(i=0;i<lengtha;i++) 
    { 
        temp=a[i]-'0'; 
        numa[i] = temp; 
    } 
        for(i=0;i<lengthb;i++) 
    { 
        temp=b[i]-'0'; 
        numb[i] = temp; 
    } 
    for(i=0;i<lengtha;i++) 
    { 
            suma = suma + numa[i]; 
    } 
    for(i=0;i<lengthb ; i++) 
    { 
        sumb=sumb+numb[i]; 
    } 
    sum = suma * sumb; 
    printf("%d\n",sum); 
    } 
}