Why doesn’t my summation work?

Question

I have this activity:

Write a function that receives, as input, a vector of n > 0 elements of type Cell and return, as output, the sum, of the weights of all vector elements belonging to bands. For example, for the sequence "yyzzzya", if the weights of these elements are 10,2,5,4,5,4,3, their function must return the value 26.

I start it with the 7 elements, put the same char in the description and the int but when sum me the value of 21; here is the code

#include <stdio.h>
#include <stdlib.h>
typedef struct {
    char car;
    int peso;
} Cell;

void SomaDosPesos (Cell vet[],int tam);

int main(){
    int i,tam,a1;

   do
   {
        printf("\nDigite a quantidades de elementos que ira inserir, tem de ser maior que Zero! :"); 
        scanf("%d", &tam);
   } while (tam < 0);
   
    Cell  vet[tam];

    for(i = 0 ; i < tam; i++){
        
        printf("\nDigite um caractere:");
        scanf("%s",&vet[i].car);
        

        printf("\nDigite o peso deste caracter:");
        scanf("%d", & vet[i].peso);

    }
    SomaDosPesos(vet,tam);
    
}

void SomaDosPesos (Cell vet[],int tam){
    int i,aux = 0;
   
    for(i= 0; i < tam ; i++){
        printf("\nFuncao:%c,%d",vet[i].car,vet[i].peso);
    }
    if(vet[0].car  ==  vet[1].car){
           aux += vet[0].peso;
        }
    for(i= 0; i < tam ; i++){
        
        if(vet[i].car  ==  vet[i+1].car){
           aux += vet[i+1].peso;
        }
    }
    printf("\nFuncao peso: %d",aux);
}

Answer 1

solved:

for(i= 0; i < tam ; i++){
        if(vet[i].car  ==  vet[i+1].car){
           aux += vet[i].peso;
           
        }else if (vet[i].car  ==  vet[i-1].car){
            aux += vet[i].peso;
        }
    }